This seems to be a big argument these days. Some Carolina fans feel that beating a national power like Alabama or Florida is more important than winning the Palmetto Bowl. Other fans feel that winning the in state rivalry should be the number one priority. There are valid arguments for both sides.
The recruiting argument is the most prominent, and this one goes to the fans who feel that being competitive in the SEC is more important than beating Clemson. Some people feel that beating Clemson would be such a boon for in state recruiting that it's more important than beating an out of state power.
The fact is, the Clemson game isn't that important for most recruits. Kids in this state grow up dreaming of either running down the hill at Clemson or coming out of the smoking tunnel at Carolina while 2001 plays. The results of the in state game don't change a the way a player was raised. If it did, Carolina would never get any recruits in state, since they are the perennial losers of the rivalry game.