Well, all right, but this isn't the 40's/50's, this is modern day. Anyway, what possible reason do we have to believe that Peter is circumcised? There's a much simpler explanation - Peter is a fifteen-year-old kid in the middle of puberty, and Logan is an adult stuffed full to bursting with testosterone. There's a certain development that goes on there - Wolvie's tallywhacker is probably a good deal more, eh, sizable than Petey's.