There are 9 different AI personalities in Galactic Civilizations II.  Which makes debugging oh so fun.  But there are significant advantages to it as well.

First question, why write 9 different AI personalities? Most games have one.  The answer to this is because in a single player game, players usually find a weakness in a given AI and then it's boring.  So we coded up 9 different ones.  They are all derived from the same base class so there are a lot of similarities, but there are many differences too.

It's fun to test to see the AI play against itself.  See each one do their thing:

Watch the Drath manipulate other races to declare war on each other.  Or see the diplomatic Terran Alliance (the humans) build up coalitions to win.  Or of course, the Drengin, grinding one civilization down after another. 

So who wins? It really depends on the game.  It's usually quite amusing to watch the Torians and the Drengin start out near each other.  The Torian AI is very unstable (strategicaly I mean) so they will often do very well or crash and burn.

In the 10 games I've had them play each other, the Drengin have won twice, the Humans have won twice, the Drath have won once, the Korx once, the Torians twice, the Altarians once and the Iconians once.

But this was on a medium galaxy.  Different sized galaxies yield different results.