Instead of different societies with similar characteristics, each Alpha Centauri faction has distinct strengths and weaknesses. You have more control over governance. You make economic, social, and ethical decisions. Ruthless or idealistic. Devout believers or atheists or somewhere in between.
Victory can come through brute force or peaceful negotiations.
The multiplayer mode will have the same winning conditions, but you can start with a smaller world, which means you'll meet other players sooner. Even though Alpha Centauri is a turn-based game, to speed things up in the multiplayer mode, everyone takes his turn at once. Nevertheless, online games may take many hours to complete. Rather you will encounter an alien ecology that doesn't necessarily take kindly to your efforts to terraform it. That extra level of complexity reflects Reynolds' own eclectic background.