I can only speak from my experience. I'm pretty carefull about my equipment, but at times I have been careless, too. I have a bad habit of laying my Provari on a bench in the dressing room at work. The Provari has rolled off a few times onto hard tile floor. Twice this has happened with another manufacturer's tanks, and they shattered each time. The vendor of those tanks sent me a new tank free to trial, saying that he had changed suppliers and his new tanks are of better glass; I've not had the "opportunity" to test those tanks by dropping them on the tile floor, as I have gone to using a smaller mod and therefore no longer use the larger glass tanks that that manufacturer sells.
The IBTanks have had the same misfortune of rolling off the bench, but they have not cracked or shown any sign of damage. They also have survived falling from my lap onto the parking lot driveway when getting out of the car, again no problem of cracks or damage. Having said that, they are glass, and I try to be more attentive to avoid potential accidents.
Judging from my experience, depending upon the quality of the glass, pyrex can be quite durable. Are these glass tanks as durable as an all-metal or a tank that uses polypropylene for the tube, probably not. If you bring your tank into a hazzardous environment or are a total klutz that frequently drops their PV, then maybe glass is not the right material. But occassional falls onto carpet does not bother me in the least.
I have heard of some people placing a simple o-ring around both ends of their tanks, so that should their be impact contact that the o-rings are able to absorb some of the impact to avoid damage to the glass. I've not tried this myself.