The Whitestone Dome is probably the best one (and the easiest to apply and get to stick all around) but, as with all other glass screen protectors, it doesn't protect against all scratches (diamond and carbide scratch glass protectors easily) and it doesn't protect against breakage if you drop the phone.
For my money, if the protector protects against reasonable scratching, and doesn't show finger-rubbing (and adheres to the entire screen with no bubbles or rainbow effect), that's as good as it gets. And there are some cheap ones that will do that.