Presumably, the main things governing whether people want to claim are how much they like solving setups (rather that just trying to catch people out for "sounding scummy"), and how much extra information they feel their role gives them compared to what they think the average role will have.
Scum is clearly at an advantage for the latter point, because they get to know what the roles of themselves and their three buddies are, assuming they're all in a faction QT. Though 4/14 scums seems pretty strong, especially when they can essentially eat the roles of the rest of us, so I wonder whether any of them start out with nerfs. Still, with them able to eat our roles, I don't think letting on the relative strengths of our powers is a good idea even if we have a decent level of protection available to help us keep strong town roles in alive townies' hands, because I don't think faust would design a game that could be easily solved by town just by revealing stuff.