Why not use well-thought-out categories instead?
I copied Romanic's stats when I copied his idea. Blame him.
The system is generally:
Town: Obvious, like Visorslash said, although there's some occasional weirdness. Generally, they're the uninformed majority, the faction that most people in the game are. They don't know who the other townies are (except maybe a mason partner or two), they don't have any kind of team abilities, and their goal is to eliminate all threats- Mafia, Serial Killers, Cults, or otherwise. Most of the time, all townies have the same VC, and either all of them win or all of them lose (or, every once in a while, all of them draw), though there may be a few rare exceptions, particularly in some of the stranger and more complex NOTW's.
Mafia: The guys trying to kill the town, and more generally, everyone that isn't them. Can be a standard mafia faction, or can be a cult or some other unusual anti-town faction like some of the NOTW's have. Usually have a VC of outnumbering or outstrengthing everyone that isn't part of their faction, or something like that. There's a few mafia factions, mostly from NOTW's, with different victory conditions (like the Saboteurs in Impending Retribution, who had a goal of destroying the ship). Basically, the big thing that makes Mafia teams different from Neutral teams is that Mafia Teams almost always have VC's directly opposed to the Town's VC, and also usually directly opposed to other Mafia teams' VC's if there's more than one. There's some neutrals they can win with (like Survivalists, for instance), but there's also plenty they can't win with.
They must be part of a team, not a solo player- that's why Serial Killer-type roles aren't mafia, but cults are (even if they only start with one player, they can make themselves bigger).
Neutral: Solo players, like SK's, Survivalists, and Jesters, are always neutral. Some teams are also neutral, if they have some kind of team VC that's entirely or mostly irrelevant to the Town vs. Mafia battle- something like the Llamas and Moose in ATPG's Holy Grail Mafia, two neutral factions who cared only about outliving the other faction, with all other factions irrelevant. Generally, they have victory conditions that are distinct from the town's, but not opposed to them, and usually not opposed to the mafia's, though there are a few weird neutral groups that can win with the town but not the mafia, but have different VC's than what the town have and don't necessarily win just because the town won.
Unlike the other two groups, Neutral individuals and teams can, in certain cases, win the game even if they and their entire team are dead (and, in the case of Jesters, that's usually the ONLY way they can win), whereas Town and Mafia groups almost always can't do better than a draw without at least one surviving member, and complete elimination is usually a loss for them. Even for Neutrals, winning in a case like that is pretty rare.
