Melee to gunpowder warlord.
The most balanced warlord, can be highly effective in all combat situations from defending to attacking
Str: The advantage of this warlord is balance, the unit can take advantage of terrain bonus's + promotions to give it unmatched def strength in the right terrain, it's ability to access both assault (via melee) an defensive (via gunpowder) promotions means it can be equally effective at holding a defensive postion in hills an woodland, as it can be at attacking cities via it's city raider 3 promotions.
weakness: lots of promotions and only 1 attack mean this unit takes time to achive it's potencial.
Tanks
Strong assault warlord, very good offensively especially vs cities
Str: Well promoted with city raider + other promotions an these units give unmatched attack odd's, A well promoted tank can easily get 99.9% odd's (these odd's give pretty much guranteed wins, so no chance of loss, and is what you shoud be aiming for when you attack with your warlord, anything less should be left alone unless it's a dire emergancy, or you dont mind interupting the flow of play to reload, i dont like reloading so i use 99.9 odd's only) on even veteran city defenders with no need to do anything, other than just reduce the cities inherant cultural def a little bit, blitz + extra move means 3 attacks per turn, fast level up speed.
weakness: cannot use terrain def bonus's so it's defensive power (combat bonus's) is a lot less than it's city attack power.
Artilery
Good assault warlord, strong offensively and can reduce city defenses which is always a good thing, does'nt need a huge number of promo's comparitively speaking to get to full str.
Str, it's great having a warlord that can bombard + cause collateral, since it makes it much easier for all your other warlords/troops to then get there kills in, treb onwards all siege units tend to be pretty strong an offer strong str against cities, the 2 things i most like about the siege warlord is if you have a nice tasty easy target, you can hit it with your siege an then hit it with another warlord, they dont compete for the XP since the siege will not destroy the unit, so 1 enemy can level up both your siege an another warlord, you can also just hit the same weakened city defender with just you siege unit turn after turn, which will let you level it up nice an fast, siege units are actually stronger than they look str wise, since a sige unit only does a % dmg it's odds are better for the same fight, example a stock cannon 12 & a stock grenadier 12, if the cannon attacks the grenadier it's odd's are better than 50/50 since it only need to knock 80% of the health of to win, so it gives the odd's of a higher str unit because of this.
Weakness: 1 attack so slower to level up, str rating is not top tier, although due to the way siege combat works it's a little better than it looks on paper, unit gets no terrain bonus's.
Gunship/knights
lots of moves, Lots of attacks, can cause flanking damage, excellent tank killer.
Str, lots of moves, and attacks means this unit can really promote quickly, very mobile, as a cavalry unit this can be upgraded to commando (can only get before gunship upgrade) , this gives the gunship a huge number of moves in enemy terrain, you can attack, pillage squares or units that are deep inside enemy teritory an then skip back to safety that very same turn.
Weakness, no good vs cities, base str quite low
Ships, well cant comment to much here, since i always felt a land based warlord was a much better investment, however the new patch is adding the blitz promo (about time) to ships, this means all ships will get multiple attacks an should alow you to leverage the extra power of a warlord by being able to attack with it multiple times per turn, i think i will be using naval warlords more in my plans once version 3.13 ships
make it worthwile even in a tank stack. The healing rate is just wounderful, even in enemy territory.
