So you're not talking about actual guns, just theoretical ones?
The reality is that if you built two 1911s - one in .38 Super and the other in 9mm - then fired the same number of rounds loaded to the same velocity, you wouldn't see any real difference in gun life. Unless you're saying that the 9mm +P pressures are going to split the chamber eventually, the wear and tear comes form the recoil impulse, not the peak pressure. But the chamber isn't going to split and the gun won't behave differently between the two.