Dunno, just my personal observation is that the heavier the phone is the more likely it is to crack, just from the sheer amount of mass the case has to dampen. I've seen heavy phones, in protective cases and even those marketed as "rugged" crack from minor falls, and lightweight cheap shit survive the nastiest of falls. What you're probably referring to is those cases with thick rubber pads on the corners, but most cases are like half a mm thick wraps, which, IMO, won't help squat in a fall.