The factions are decent, but they are just a more extreme version of the original smac factions.
Domai is Like hive: high production, lower science
Cult is basicaly Gaia on steroids.
Cyborgs are zakharov science + gaia efficiency and none of their weakness
Usurper is Miriam on steroids
Data angels is miriam + morgan in terms of probes usage.
Sven is a naval version of morgan, but without hub restriction.
Drones is a very good faction. One of the top 3 human factions imo.
Cyborgs cant pop boom, which makes them worse than both gaians and university.
Planet cult is easily the weakest faction, unless you can worm-rush your nearest enemy.
Aliens are of course very powerful, which is why they are locked in war with eachother. They can be very hard to deal with if you start next to them.
Data angels are decent, but not a top faction imo. Probe teams are nice, but the +probe does not have that big impact.
Svensgaard is just unfair, which is why I never used him (single player and multiplayer). Starting on water gives you ~100 turns with free expansion and no war, which is just unfair.
My top 3 factions (not counting the Pirates) for large/huge maps:
University
Peacekeepers
Drones
On smaller maps Hive and Miriam really shines, however, Drones are likewise a force to be reckoned due to the nice production and starting tech (synthmetal).