God, I hate doing this, but here goes....
The Probowl is by no means a measure of each conferences strength. It's well known that most plays (offensive and defensive) are watered down to prevent injury and most players are just out there to relax and have fun. When was the last time you saw an all out blitz in the Probowl? If you ever watch the game, it's blatantly obvious from player interviews and the like that the guys are just there having fun and not seriously trying to win.
With that being said, the winners and losers over the last few years:
2006 - NFC 23 - AFC 17
2005 - AFC 38 - NFC 27
2004 - NFC 55 - AFC 52
2003 - AFC 45 - NFC 20
2002 - AFC 38 - NFC 30
2001 - AFC 38 - NFC 17
2000 - NFC 51 - AFC 31
So, if you take this decade as an arbitrary cut off, the record is AFC 4 wins, NFC 3 wins. So, how is the NFC superior based on Probowl wins? Clearly, they're not.
The whole point of the Superbowl is to determine which conference is better. That's why they played the game in the beginning. It's a true playoff scenario with seeding and brackets, supposedly to get the best AFC team to play the best NFC team; and then ultimately they play each other to see which is best - AFC or NFC. So, to say the Superbowl doesn't matter is not undersanding what you're talking about. To say the Probowl, a game everyone involved with readily admits they don't play their best, is the only game that truly guages conference strength further illustrates a fundamental lack of knowledge on the subject.
OK... So that's all I have to say about that.