Sid Meier's Alpha Centauri/Factions

All factions have distinct advantages and disadvantages. They have different society traits, start with different technologies, and sometimes even have oddities such as smaller maximum base sizes. This means that every faction has a different overall playstyle, although some factions are more suited to some play styles than others. For instance, the Hive is more likely to ICS than the Peacekeepers, because Yang gets free Perimeter Defenses but little energy income, while Lal can get more population per base and may want to take advantage of it.

The game settings can enhance or reduce the advantages and disadvantages of each faction. For instance, disabling Blind Research weakens the aliens of Alien Crossfire because they never have Blind Research, so they lose one of their inherent advantages (Or rather, non-alien players gain the same advantage the aliens already have). Likewise, Svensgaard would prefer a world with massive oceans (essentially more territory for him) and arid terrain (which hurts land factions much more than the sea-based Pirates), while all other factions would probably prefer the opposite.

The factions
A table comparing all the factions follows. Note that a faction's "preference" is preferred by the AI but a human player can (and, under some circumstances, may want to) use something else. However, the faction's aversion, if any, is always enforced: a player may never choose a faction's aversion. It simply will not show up in the Social Engineering table.

[1] Most factions have "0 hab", meaning it can have up to 7 citizens before requiring a Hab Complex. Morgan has -3, so his maximum is size 4 before Hab Complex, and Lal has +2, meaning his maximum is 9. The Hab Complex always boosts the limit by 7, so afterward the limits are 11 and 16 for Morgan and Lal, respectively. Of course, all limits disappear when a Habitation Dome is built.

[2] Net negative modifiers to efficiency in Social Engineering are ignored, while positive modifiers still take effect. Yang's bases can still suffer from inefficiency.

[3] First base and starting units are in the sea. Ocean shelf tiles produce +1 mineral. Can improve non-shelf ocean tiles with Advanced Ecological Engineering.

[4] Alien factions all have a free recycling tank in every base, energy grid in lieu of commerce (every two facilities adds +1 energy per turn; secret projects add 2.5 energy per turn), Space Survey (all land masses revealed at start) regardless of game settings, non-blind research regardless of game settings. Alien factions start with Progenitor Psych and Field Modulation and have permanent vendettas against all other alien factions, even custom ones. Alien factions can win by building Subspace Generators in each of 6 cities of size 10 or greater. The Manifold Nexus landmark grants alien factions +1 Research as well as +1 Planet.