I'm assuming you're askig about good ol' PETE, aka Better Bottles?
The advantage is quite simple, a cracked Better Bottle won't rip through your veins, harm your kids or pets.
I'm a Better Bottle fanboy, I've got a glass carboy, plastic bucket fermenter and myriad of Better Bottles. I certainly use the carboy and the bucket, but I strongly prefer the BB's, and theyr'e what gets added to my equipment list, not glass.