Goodness, I loved this game so much. As far as how well they were written, I loved the Believers, tbh. Miriam may seem like a standard issue fundamentalist at the beginning of the game, but by the end, her premonitions seem positively prophetic, and she's suddenly sounding like the voice of reason. To play, I was almost always the Gaians, Peacekeepers, or University. I think the Gaians were most fun to play in order to grab mind worms from the start.
Wow. I never played the Believers, so that's a real unexpected POV for their truly turning out "prophetic".
I almost (entirely?) chose those three factions as well, but primarily preferred Lal and the UN for their fundamentally humanitarian and democratic mission, even with the bureaucracy.
I always wondered how the Gaians would be different in this regard, as their pacifist nature wouldn't combine well with a strong(wo)man regime. Perhaps enviro-absolutism would make the Takings Clause and Due Process on such issues basically non-existent, even if the rest of their domestic society was a liberal democracy?