Blue Duck ,
Purchased my P9 almost exactly a year ago as a CCW for when the weather in southeast VA dictated attire which made concealing my P7M8 or Glock 19 difficult. Put about 1200-1300 rounds through it in the first 2 months. This included a good sample of 124 and 115 gr +P. Haven't shot it in a while since I'm now in a very different climate. Total round count is @ 1400. I have noted minimal mechanical wear on the pistol and no failures except for a couple of isolated feed stoppages with a single type of ammunition. I found the real limitation on extended and/or extensive shooting with the P9 was the wear and tear on my hands! A FIRM grip made of the most comfortable shooting. It was easy to get lazy after a few hundred rounds, however, and the reward was a noticeably sore hand.
Comparing the P9 to the G19, I would point to two major areas of difference. First, the P9 really is a compact pistol made for CCW. The G19 is in a different size class. It's certainly concealable and "compact" in comparison to the G17, but the G26 might be a more comparable size to the P9. My G19 does not provide the same care free concealment in a bellyband under a t-shirt that my P9 allows. The second area of difference pertinent you your question - the G19's been around quite a bit longer than the P9 and thus there is a greater data pool to use in judging "longevity" or durability. With the P9, you're extrapolating based on what you can determine from its design and limited record. With the G19, you're able to draw on a significantly longer and wider track record. While I strongly suspect that my P9 will last many thousands of rounds and days of carry, I KNOW that many other G19s just like mine have done so.
Just my $0.02. If it helps at all, I'd happily buy the P9 again if my intent was a gun to be carried a lot AND shot a lot.