In
Benchrest the goal is accuracy. You want to use a case and caliber that doesn't beat you up over the course of a 5 target match plus one slighter target, and you want to take advantage of bullet diameter. In IBS score shooting, the only sanctioned benchrest in Maine, that means 30 caliber and the BR case in VFS or one that meets hunter class case capacity rule in the six power scope game if you want to shoot hunter or a BR if you aren't chasing hunter records.
There are occasional 6 PPC shot but they are the exception. I'm not trying to discourage you from a PPC if you want to varmint hunt or have some occasional fun off the bench. But if you really want to shoot sanctioned benchrest think 30 caliber. Don't waste your money on a PPC. Go to some matches, look, ask questions. Most will gladly share info with you.