I've used the Zagg protectors for years. I used the glass protectors on my iPhone 6 plus. I had to replace it about 5 times over the past year due to cracks in the glass and chipped edges. This did not occur due to drops or mistreatment of the phone.
By the way, I spoke to someone at the Zagg kiosk and they said the current glass protectors work fine with the new 6s models. But I am hoping that Zagg comes out with a thinner, more durable glass protecter.
I am also looking for another type of protector for my 6s plus. Something that is thinner than 0.4mm and perhaps is curved to accommodate the curved iPhone screen. Still searching......