IMO, a scum den is a better teacher than a PR den.
The PR's are worried about how to help the town, which is harder than taking it down. They discuss how they're going to help the town and blah blah blah.
Being scum, IMO, can be simpler. You have to take out good guys. There's more time to focus on new players.
In my most successful game, which was my 1st, I was scum. I was (very well) coached by Lab Rat. We won.
you do know that scum is a PR role too.