The AI in GC3 is worse than it was in GC2! Playing on a large map, default settings, tech trading disabled, 6 random opponents on "Incredible" setting, and it wasn't even close.
The AI is slow colonizing planets, will always give you money for resources (even when it has more than it needs), and if you have at least 3,000 credits, you can get a war started.
I've always played with tech trading disabled, because it's so broken, and I almost feel like boycotting resource trading.