3 ways South Carolina football would benefit if Clemson joined the SEC:
The path becomes more difficult for the Tigers
The first and most obvious benefit for the South Carolina football program, as far as the rivalry with Clemson is concerned, is that the Tigers should lose more if they joined the SEC.
Without much exception, an SEC schedule is tougher than an ACC schedule. Both leagues play eight games during conference play, but the SEC strength of schedule is more difficult because the league is better.
Theoretically, that means that Clemson's clear path to 10+ wins would be over with a move to the SEC. It doesn't mean that they couldn't still accomplish the feat—the Tigers are a good program—but things wouldn't be as easy.
In the history of both conferences, the SEC has won over 64% of its games against the ACC. Clemson has, in its history, lost about 60% of its games against the SEC, too, including a 7-10 mark against the league in postseason play (bowl games and the College Football Playoff). Those numbers are better in recent years (22-17 against the league in their last 39 tries), but their success rate is far worse against the SEC than their 122-32 mark against ACC teams during the same span.
Clemson would lose more in the SEC than they do in the ACC, and while that is good for the emotional health of South Carolina football fans everywhere, it also would help close the gap between the two programs that has developed over the last decade.