Balancing games is an interesting challenge. Best case scenario, town can annihilate the mafia, if they get really lucky, due to greatly outnumbering them. However, town is rarely that lucky.
When I rate the difficulty of a game I'm designing, I check to see how many mistakes the town can make before they automatically lose.
In a game like.... Godfather III, there were 3 mafioso. But there were also a lot of townies. You could make 5 or 6 mistakes and not have it really affect the game. And, one lucky shot could reduce the ability of the mafia to kill more than once a night, giving the town additional chances. A game like that is difficult for the mafia to win.
In a standard mini game (6 town, 1 mafia, night kill) that means 1 mistake, 2 townies dead. (nightkill). That reduces the game to 4 townies, 1 mafia. 2 mistakes mean another townie dead day phase, another dead night phase. That brings it down to 2 townies, 1 mafia. 3 mistakes mean the town loses. Of course, that means the mafia has to play a perfect game to win, that's difficult.
In a more difficult mini game (5 town, 2 mafia, no night kill) That means 1 mistake, 1 townie dead... 4 town, 2 mafia. Another mistake, and another townie dead.... 3 town, 2 mafia. At this point the mafia nearly takes up half the town, and all 3 townies must choose correctly, and no divisions among their ranks... the final round is very hard. So it's easier for the mafia to win.
A very difficult mini game (5 town, 2 mafia, 1 night kill) means 1 mistake, 2 townies dead... 3 town, 2 mafia. This means unless town gets it totally right and all townies unite against the mafia on the second round, the mafia wins. It's very difficult for the town to win, because even if they get it right one round, it is not over, and the mafia still can murder. It basically works out to allowing one serious mistake by the town, on round one no less.
Now, take away the ability of the mafia to kill, but give them a conversion and make them a cult, and it works out to 2 mafia, 5 town. One mistake, and it is 3 mafia, 3 town. That's game over, assuming the cult converts properly and votes intelligently.
---
After that, you look at best case scenarios. In the best of the best cases, the town kills a mafia every day phase. Usually it shouldn't take more than 2 or 3 correct guesses for the town to triumph. It is the fact that they are divided and suspicious of one another that makes it difficult for them to guess correctly.
What makes the game difficulty difficult to predict is the existence of protown roles like a detective who may be useful, or may never find the mafia, and die early. Or, two or more anti-town groups in competition with one another. So long as 3 or more groups exist, it is possible for the town to triumph in almost any situation... even if they are greatly outnumbered. See Treehouse of Horror for the town getting crushed by mafia, until the mafia obliterated one another, leaving the fate of the game in the hands of one townie.
Things such as total or partial invulnerability greatly affect the balance of power. For example, in the Council of Villains game, not only did the Bowser character have total invulnerability (itself an insane trump card), but there ended up being at least two protector roles. The protector roles could, in theory, defend one another. And that's exactly what happened. Eventually there were at least 3 totally indestructible people in any given night phase. There was an amazing amount of mafia or anti-town in that game but... the town was given considerable advantages.
In my opinion, the most powerful townie is the defender/immune/invulnerable role, and the most powerful mafia is the cultist. Any of these things upset the balance of power in a huge way. The investigator is also a powerful role, but more difficult to predict in terms of usefulness.
Bookmarks