All guns can break. All guns could jam.
In my local IDPA matches, I've never seen one of the 3 P7's hiccup. I've seen (and had) Glocks jam, and I've seen broken trigger springs in Glocks, tying them up (another reason for the NY trigger).
Does that prove anything? Of course not. They're both far more reliable designs than something like a 1911.
As far as the grip pressure, both the P7 and the Glock require a firm grip to function properly. I don't know about shooting a P7 "all day" as I've never shot a single firearm for more than a couple of hours. But I'm sure someone could come up with a reasonable situation requiriung 8 hours of constant firing. I can't.
Another advantage of the P7 that I forgot to mention is that the blowback design avoids failures to extract, or double feeds. The cases are self extracting, unlike the Glock that requires an extractor to pull the case out with the recoiling slide. Probably another reason the P7 seems so reliable.
Since someone mentioned the P5, my brother has one. His test target is a 3 inch group. My P7 test target is a 1 inch group. My trigger is better too.
Even Jeff Cooper likes the P7.
The European and US agencies who did spend the money have been very happy with the P7. New Jersey has worn theirs down and doesn't like the cost for rebuilding. So they chose the S&W99. Then they sent that back and bought Sigs. The Sig is a good gun and while pricey, will still make the budget minders happy. They did not choose the Glock.