I've run PtA as a convention game four times now. The first two times we came up with a show concept, fleshed it out a bit, and then the players all made their own protagonists. They talked with each other about their characters, so they weren't made in a vacuum, but this was mostly individual effort. While it worked out fine, people struggled coming up with with Roles and Issues.
The last two times, we made separate lists of Roles and Issues on the white board that would suit the show. Then each of the players claimed one of each and made their protaganist (and I'd draw lines between their Roles and Issues on the board). I think the result was characters that were more interesting and better connected to the premise. It also made character creation faster as there was no one left struggling for an Issue or a Role.