The biggest advantage is to the Pro Bowl, not the Super Bowl. However, there aren't really any disadvantages to the Super Bowl, either. (At worst it makes no difference, as you argue, and at best it adds even a little more excitement/visibility.)
As is, the Pro Bowl is basically irrelevant to everybody but the players (and even to some of them). Moving it before the Super Bowl is a worthy attempt at making it relevant to fans as well:
- The Super Bowl is the climax of the season. When it is over many of the fans don't care about football any more. That is why it should be the end of the season. *PRO*
- In the two weeks between the conference championships and the Super Bowl, the fans are hungry for NFL news. Almost all of that news is about the Super Bowl teams, and is often barely relevant or pretty dumb. Adding the Pro Bowl in that spot provides something for all NFL fans (especially those of teams not in the SB). It is also something that is arguably more fun and relevant than the normal NFL news at that time. *PRO*
- Players from the Super Bowl teams can't play in the Pro Bowl. *CON*
On that last point, Super Bowl coaches don't go to the Pro Bowl (conference championship losers do). Also, many Super Bowl players skip the Pro Bowl even if they're invited, so while it is a con it is not as bad as it would seem at first glance.
Did I miss something else?