My highly unscientific viewpoint is that this seems to be a trade off between durability and traction. The harder the tire, the longer it takes to thin out the tread, and the more "puncture resistant" that tire is. The thing is, that the harder compound tires tend to give poorer traction, which is something I'm much more concerned about when descending or riding in the wet. I've ridden pro3's for several years and have had pretty good experiences, some flats, but not a lot. I do think that they tend to attract small sharps (little bits of glass etc), especially in the wet that exacerbates problems if you don't inspect your tires. I routinely go over my tires every few days with a flashlight and a small screwdriver to dig out small sharp rocks, glass fragments that could become a puncture if they work their way through the cords. That and proper inflation pressures seem key.

Having said that, I've preferred riding Michelin Krylions on the winter in NorCal as they do have a longer lifespan and seem almost as grippy as pro 3's. All of this is now moot of course, as Michelin has switched things up with the Pro4. I have a set of Pro4 endurance tires (the Krylion replacement) in my garage ready for winter duty as soon as I can wear down my current Krylions.