unless its a Spurrier, Saban, Petrino type hire where the coach has already demonstrated a high level of success at the college level as a head coach. Given the failure of the Shula and Croom experiments in the SEC, it would be best to stay away from NFL assistants or even HCs that haven't been around college in the recent past. They are totally different jobs. Heck, look at the horrible job the ND coach is doing who came from the Patriots.
Pros- Players pretty much show up in the draft with a combine report and a bunch of college video clips
College- Coaches must look at all the above + Call the players to set up campus and in-home visits + Make sure they commit + Call back to insure they stay committed + Hope they sign with you in Feb.
Even Croom said that its difficult in college because you must foresee your weaknesses a couple of years in the future, where in the pros you just make trades or pick up free agents. (Not worded exactly but i believe he said it after his second season)
Maybe they learn more about the actual gameday coaching in the NFL, but then come back to college where they enjoy it more or something. Carroll, Butch Davis, hell,, even Wannstedt is having a good year this year.
succesful college career at The U, then with the Cowboys. You could argue Barry Switzer. He won a Super Bowl with a good team, but was the coach when the dynasty began to fall apart.
Either way, its rare that people succeed at both levels.