Since Conquests provides two new difficulty levels to play it, it seems a good time to take a look at how they stack up, and whether there are any changes to those older difficulty levels. Running through the editor for both Play The World and Conquests, we can see just how hard the new levels are.
There appear to be only two changes in the editable difficulty level variables between PTW 1.27 and C3C 1.0, and they are both at the Deity level. In PTW, the Deity AI to AI trade rate is at 160, while in C3C it's at 170. Also, in PTW the percentage of optimal cities is at 70, while in C3C it's at 60. Both these changes make sense when fitting Deity in between the Demigod and Sid difficulty levels added in C3C. All the lower difficulty levels look to be the same, and the two new levels fit well within the natural progression in difficulty. The Sid level looks to be exceedingly brutal: it starts with a ton of extra free units, and essentially never has to pay for unit upkeep, no matter what government it's in, because of all the free support; the cost factor and AI to AI trade give it a wicked kick as well.
Keep in mind that by default the AI civs play at the Monarch level (or did in PTW, and most likely still do) for the purposes of the lower four variables (Citizens born content, Citizens quelled, Attack bonus vs barbs, Percentage optimal cities.) This, apart from all the other direct bonuses they receive, makes life easier on the AI civs when the human is playing against them on a higher difficulty level; they will be able to grow a bit further without worrying about unhappiness because of the citizens born content, and so forth.
Below I've listed the information directly from the Conquests editor in a chart format. The explanation below the chart is directly from the Civ3QEdit help file, and explains each of the variables. One correction to that information: despite what the help implies, in the default rules start unit type 1 is a settler and start unit type 2 is a worker, not vice-versa. So a Sid level AI civ starts with 2 free settlers and 4 free workers, not the other way around, which is no doubt a very good thing.
Civilizations III Conquests 1.0
Number of Defensive Land Units (Additional AI Starting Units)
Determines how many extra defensive land units the AI will start with on the selected difficulty level. To determine which unit is used, the AI will determine which available unit (e.g. units that can currently be built) is its best defender.
Number of Offensive Land Units (Additional AI Starting Units)
Determines how many extra offensive land units the AI will start with on the selected difficulty level. To determine which unit is used, the AI will determine which available unit (e.g. units that can currently be built) is its best attacker.
Number of Start Unit Type 1 (Additional AI Starting Units)
Determines how many extra type 1 start units the AI will start with on the selected difficulty level. This corresponds to the default start unit 1 on the general settings page (normally a worker).
Number of Start Unit Type 2 (Additional AI Starting Units)
Determines how many extra type 2 start units the AI will start with on the selected difficulty level. This corresponds to the default start unit 2 on the general settings page (normally a settler).
Additional Free Support (AI Unit Support Bonuses)
Determines how many extra units the AI can support, in addition to any existing governmental bonuses, on the selected difficulty level. Note that this number is cumulative with all other support bonuses.
Bonus for Each City (AI Unit Support Bonuses)
Determines how many extra units the AI can support per city, in addition to any existing governmental bonuses, on the selected difficulty level. Note that this number is cumulative with all other support bonuses
Max Government Transition Time (AI Bonuses)
Determines the maximum number of turns the AI must remain in the transition government type (default is Anarchy) before transitioning to the newly selected government type. Setting this number lower will reduce the negative effects of switching governments. The default value of zero means there is no maximum to how long this can take.
Cost Factor (AI Bonuses)
Determines the cost factor that is applied to AI growth, shields, and research. The player's cost factor is always 10. Choosing a value higher than 10 means the AI will be at a disadvantage, while choosing a value lower than 10 means the AI will be at an advantage.
AI to AI trade rate (AI Bonuses)
Determines the percentage multiplier used in AI AI trade sessions on the selected difficulty level. This value is a percentage (acceptable values range from 100% to 1000%) which is multiplied by the total value (in gold) of the initiating civs offerings, which is used by the "other" AI civ to determine whether a deal is acceptable or not. For example, with a rate of 120, an AI civ offering 100 gold to another AI civ for something would actually be worth 120 gold to the other AI civ.
This rate directly affects the frequency and aggressiveness with which AI civs trade amongst themselves.
Number of Citizens Born Content
Determines how many citizens in a new city are born content for the selected difficulty level. The lower the number, the more difficult the game will be.
Number of Citizens Quelled by Military
Determines how many rioting-citizens are quelled with the presence of military units.
Attack Bonus Against Barbarians
Determines the attack bonus enjoyed by any player (human or AI) against barbarians. A value of zero means the barbarians have no combat disadvantage, thus a barbarian warrior would be as powerful as the warrior of any player in the game.
Percentage of Optimal Cities
Determines what percentage of the optimal number of cities setting (found on the world sizes page) is actually optimal on the selected difficulty level. If this value is 100%, the optimal number of cities will be equal to the default setting for the given world size. At 50%, the optimal number of cities is halved. At 200%, the optimal number of cities is doubled. This value will not match the value on the World Sizes page exactly because the corruption setting of the player's government type is also a modifier.
There appear to be only two changes in the editable difficulty level variables between PTW 1.27 and C3C 1.0, and they are both at the Deity level. In PTW, the Deity AI to AI trade rate is at 160, while in C3C it's at 170. Also, in PTW the percentage of optimal cities is at 70, while in C3C it's at 60. Both these changes make sense when fitting Deity in between the Demigod and Sid difficulty levels added in C3C. All the lower difficulty levels look to be the same, and the two new levels fit well within the natural progression in difficulty. The Sid level looks to be exceedingly brutal: it starts with a ton of extra free units, and essentially never has to pay for unit upkeep, no matter what government it's in, because of all the free support; the cost factor and AI to AI trade give it a wicked kick as well.
Keep in mind that by default the AI civs play at the Monarch level (or did in PTW, and most likely still do) for the purposes of the lower four variables (Citizens born content, Citizens quelled, Attack bonus vs barbs, Percentage optimal cities.) This, apart from all the other direct bonuses they receive, makes life easier on the AI civs when the human is playing against them on a higher difficulty level; they will be able to grow a bit further without worrying about unhappiness because of the citizens born content, and so forth.
Below I've listed the information directly from the Conquests editor in a chart format. The explanation below the chart is directly from the Civ3QEdit help file, and explains each of the variables. One correction to that information: despite what the help implies, in the default rules start unit type 1 is a settler and start unit type 2 is a worker, not vice-versa. So a Sid level AI civ starts with 2 free settlers and 4 free workers, not the other way around, which is no doubt a very good thing.
Civilizations III Conquests 1.0
Code:
Chief. Warlord Regent Monarch Emp. Demigod Deity Sid
[b]AI Bonuses[/b]
Def Land Units 0 0 0 2 4 6 8 12
Off Land Units 0 0 0 1 2 3 4 6
Start unit type 1 0 0 0 0 0 1 1 2
Start unit type 2 0 0 0 0 1 2 2 4
Extra free support 0 0 0 4 8 12 16 24
Bonus for each city 0 0 0 1 2 3 4 8
Max gov transition 0 0 0 4 3 2 2 1
Cost factor 20 12 10 9 8 7 6 4
AI to AI trade 110 120 130 140 150 160 170 200
[b]Other variables[/b]
Citizens born content 4 3 2 2 1 1 1 1
Citizens quelled 1 1 1 1 1 1 1 1
Attack bonus vs barbs 800 400 200 100 50 25 0 0
Percent optimal cities 100 95 90 85 80 70 60 50
Determines how many extra defensive land units the AI will start with on the selected difficulty level. To determine which unit is used, the AI will determine which available unit (e.g. units that can currently be built) is its best defender.
Number of Offensive Land Units (Additional AI Starting Units)
Determines how many extra offensive land units the AI will start with on the selected difficulty level. To determine which unit is used, the AI will determine which available unit (e.g. units that can currently be built) is its best attacker.
Number of Start Unit Type 1 (Additional AI Starting Units)
Determines how many extra type 1 start units the AI will start with on the selected difficulty level. This corresponds to the default start unit 1 on the general settings page (normally a worker).
Number of Start Unit Type 2 (Additional AI Starting Units)
Determines how many extra type 2 start units the AI will start with on the selected difficulty level. This corresponds to the default start unit 2 on the general settings page (normally a settler).
Additional Free Support (AI Unit Support Bonuses)
Determines how many extra units the AI can support, in addition to any existing governmental bonuses, on the selected difficulty level. Note that this number is cumulative with all other support bonuses.
Bonus for Each City (AI Unit Support Bonuses)
Determines how many extra units the AI can support per city, in addition to any existing governmental bonuses, on the selected difficulty level. Note that this number is cumulative with all other support bonuses
Max Government Transition Time (AI Bonuses)
Determines the maximum number of turns the AI must remain in the transition government type (default is Anarchy) before transitioning to the newly selected government type. Setting this number lower will reduce the negative effects of switching governments. The default value of zero means there is no maximum to how long this can take.
Cost Factor (AI Bonuses)
Determines the cost factor that is applied to AI growth, shields, and research. The player's cost factor is always 10. Choosing a value higher than 10 means the AI will be at a disadvantage, while choosing a value lower than 10 means the AI will be at an advantage.
AI to AI trade rate (AI Bonuses)
Determines the percentage multiplier used in AI AI trade sessions on the selected difficulty level. This value is a percentage (acceptable values range from 100% to 1000%) which is multiplied by the total value (in gold) of the initiating civs offerings, which is used by the "other" AI civ to determine whether a deal is acceptable or not. For example, with a rate of 120, an AI civ offering 100 gold to another AI civ for something would actually be worth 120 gold to the other AI civ.
This rate directly affects the frequency and aggressiveness with which AI civs trade amongst themselves.
Number of Citizens Born Content
Determines how many citizens in a new city are born content for the selected difficulty level. The lower the number, the more difficult the game will be.
Number of Citizens Quelled by Military
Determines how many rioting-citizens are quelled with the presence of military units.
Attack Bonus Against Barbarians
Determines the attack bonus enjoyed by any player (human or AI) against barbarians. A value of zero means the barbarians have no combat disadvantage, thus a barbarian warrior would be as powerful as the warrior of any player in the game.
Percentage of Optimal Cities
Determines what percentage of the optimal number of cities setting (found on the world sizes page) is actually optimal on the selected difficulty level. If this value is 100%, the optimal number of cities will be equal to the default setting for the given world size. At 50%, the optimal number of cities is halved. At 200%, the optimal number of cities is doubled. This value will not match the value on the World Sizes page exactly because the corruption setting of the player's government type is also a modifier.