I've read a lot of people selecting aggressive AIs in the custom game menu. I've never played with aggressive AIs and was wandering the reasoning to this. Is it because the diplomatic penalties that other civs give to you are either less or go decrease more quickly? Because I find it strange that people would want to increase the likelihood of going to war not on our terms but the civs.
I personally use the aggressive AI special game startup option. It makes all the AI's more aggressive, more aggressive towards the human player but also more aggressive towards eachother.
The main reason why I do this is because I want more competition and not just more competition on the economic side of the game but mainly more competition on the military side of the game. The normal AI setting makes the AI rather docile, in most cases the player can decide when wars start and there will be few to no surprise attacks. Thus the game can become a bit predictable and controllable. I however like to be surprised by the opposition, I don't like a predictable path to victory. (So your remark about "Because I find it strange that people would want to increase the likelihood of going to war not on our terms but the civs." actually applies to me, I like the challenge.)
Note also that with the aggressive AI setting, the AI is not only more aggressive, but it also creates more units. Thus the military way to control and win the game will typically become less attractive and more costly. Since most people agree that a few controlled successful military conflicts can be very beneficial to your odds of winning the game, making this path to victory more costly is in my opinion a good thing.
The main negative element of the aggressive AI setting is that the AI can relatively overspend on military slowing down their economic development. This is mainly an issue on the lower difficulty levels. On the higher difficulty levels where the AI gets economic bonuses and military upkeep is less costly, the AI can both develop its economy and create a powerful military making its opposition to human victory impressive.
The aggressive AI setting is not exactly the same as hand picking aggressive leaders as opposition. The setting not only causes more aggressive opposition but also more military spending which is of course needed to be successful with aggression. But I guess that the reason for picking such leaders would be similar to my reasons for selecting the aggressive AI option.
A question: My cat laid on the left side of my keyboard while I was playing a single player game. Somehow it switched me to playing as the AI! How do I switch back??
Ask your cat!
Sorry, I can't help you.
Why do so many people recommend against making your capital a GP Farm?
One of the main reasons would be the strong bureaucracy civic which immensely increases the commerce output of your capital. Thus it can be very beneficial to develop your capital as a cottage city especially since the cottages have a lot of time to develop since it's your first city.
Of course, you don't have to develop your first city into a cottage city. The city can be a prime GP farm location and you can move your palace to another city which you can then develop into a cottage city. With a bit of planning that can work out just fine.
The bureaucracy civic is of course also more powerful on smaller maps where the commerce output of a single city (the capital) can be more influential.