I own both a P229 SSE/9 (my first pistol) and a [P229] M11-A1 (my second pistol, purchased a couple of months after I purchased the SSE, to use for my CCW course and as my first CCW). I have 357SIG Exchange kits (and .40 S&W bbls) for both, and both pistols stay dressed, and shot, as 357SIG 99% of the time. I would be really surprised if, after shooting 357SIG from your P229, you will prefer to switch it to another caliber, cost of 357SIG ammo notwithstanding!
rx7sig