I gave my mom the iPhone 6 Plus with the Apple leather one. She says she drops the phone like three times a day and the phone has no damage to it, so I think it's pretty good. My girlfriend also has a 6 Plus with an Apple leather case and it's also working pretty well.

My 6 has a like a zillion dings on it already (and a chip on the screen), but I don't use a case and the phone is a slippery mother.