I've tried all 3, the trader has a huge advantage in terms of conventional fleets, but the other two have "come from behind" win conditions, so who knows.

I definitely feel that the trader's RO advantage is way too extreme. I'm literally barely monitoring the game in which I'm a trader, and I'm up to something like 30k RO last time I checked. As a researcher or warlord I've had to bust my ass to get even 5k RO, and that's only the result of fighting over Jovian planets that I wouldn't otherwise have.