Gliese 581
Your average civ junkie
I usually attack the other colonies even if it's not right away. They are not useful like natives, and you can actually keep the cities you capture. You don't even have to pay off/anger natives to get good lands if your neighbor already claimed it for you...
I've always found it ridiculously easy with a few cannons, but then again I have usually played on the easiest difficulty. I just wish the REF was as dumb as the other colonies were...
The difficulty level makes no difference at all.