Hello David....+P+ ammo will only increase the wear of the gun compared to standard pressure...how much is up for discussion. Although, a 115+P+ is about what a Nato 124 is pressure wise and supposedly what LE/military 9mm handguns are designed to handle and a Sig being a European designed pistol, well, I figure they're designed to operate around that pressure too. The ammo companies just prefer to restrict the sale of that pressure ammo to LE/military only because cheap made pistols (like Lorcin) couldn't handle it.
I remember reading an article about the Browning HiPower using +P ammo, in the article they fired 5,000 rds without noticeable wear. I don't know about you but I don't think I'll ever put 5K +P rds thru any one pistol...haven't yet anyway....
I have some 115+P+ and like the accuracy of them a lot, but like you, I have come to prefer the standard pressure 147 for defensive purposes....although, I'm quite sure that little screamin' 115'er would ruin someones day too!
I've shot some invading critters with that +P+ rd and it flat did a job on them but just feel better against two legged predators with that 147...for penetration and all...
Say, you ain't gonna get rid of your G 19 now are ya?? That pistol can handle anything made!
Ken