Face-to-face Mafia is certainly easier to read people in, but this actually (IMO) makes it a worse game. There are other issues as well, such as the inability of the Mafia to communicate articulately at night, but if you're a good lie detector (or the scum are bad liars) the game becomes almost trivial, and introducing the difficulties of online communication IMO adds an appealing element of challenge. That said, I agree that face-to-face Mafia with a regular group can certainly be fun and even educational in itself.