IIRC from one of aelf's tries aggressive AI is more aggressive vs the human player, not vs each other. So you'll have to work much harder on the diplomacy level to maintain peace. I don't think it's a reasonable setting to put for the first few BtS games, unless you're feeling like going for all out war for example. Against a big power rating even the aggressive AI should be a little timid.
That was warlords version, not BtS. In warlords, the "AGG AI" just had a hidden negativie diplo modifier against the human. Now they are more likely to build military units, but might not go to war. And the AI WILL fight each other more now.
Ghandi is just as likely as normal setting to not attack, but he will be more inclined to build units to defend himself.
So since this is the discussion, I have played about an equal number with and without and will share a few observations.
-The AI will attack the other AI more than it used to with this setting.(One game Monty was ravaging his continent, I should have known when I saw the flood of GG being born in other lands)
-Builder Civs will still build. Ghandi had a good defense, as well as a nice set of wonders hiding behind those walls.
-More units will be built and cities will be better defended, but not necessarily in the ancient era. It seems there is to big a window early where an axe rush is optimal (in both AGG and Normal setting) that the AI does not prioritize hooking up metal or horses and building stronger units. But once they do, their stacks are very mixed.
-Unit spam can happen, but it seems somewhat dependant on the civs around. One game I could have taken Hannibal down early(with maces and cats), but since we were on pleased terms I felt it was not needed. For the most part his cities were lightly defended, but I felt bad about backstabbing. But I missed it when our relations dropped to cautious, and our close borders were enough to make me a target. And he took the fight to me, and I missed his troop build up.
All in all, I did not see a huge difference between the two settings. Just more units. People complain about the AI teching slower, but I think that has more to do with the espionage system than the units built. I have seen just as many wars started by the AI in normal as I have in Agg.
I would suggest that you try a few games out off line to see what you think. The hardest part is every game I have played has been somewhat different, and that makes it hard to compare any two based on settings.
I think that if you do decide to try it out though for a game in your series, you should turn it on when you are a builder civ. I think it will be cool to see if you can highlight the leader traits and be a good builder in a game that is "designed" to make it more difficult.