Ive shot a bunch of +P+ out of a number of guns with no ill effects. I currently use it in a couple of Glocks.
As far as moving up to 357SIG, interestingly enough, my 31 in 357SIG showed a considerable amount of accelerated wear with factory 357SIG, than my one 17 shows (which is at this point, just some slight finish discoloring in the same spot) and it will probably pass 50000 rounds fired before the year is out. Ive fired more +P+ through the 17 than I did 357SIG through the 31 too.
I havent found +P+ is any harder to shoot with, but I do practice with fairly hot reloads, so there really isnt any difference in feel in what Im shooting in practice and what Im carrying. I seriously doubt you could tell the difference in +P and +P+ if you didnt know what was in the gun.
Now if you get out of the +P+ realm, and get into some of the SMG loaded 9mm, you may have something more to worry about. I have had a gun show pretty extreme wear, to the point of cracking the upper and breaking some other parts using some surplus Spanish stuff. Then again, it, and some of the others Ive fired over the years, make current +P+ seem like target loads.