I only really use my camera for snapchat really, so I don't need it to be amazing, from what I've heard, both the z2 and the m8 are very evenly matched, trading blows in different aspects, the only thing that bothered me about the z2 other than the pretty small power button which I could live with, was the slightly leggy loading after unlocking the phone, but I think that's probably the stock android version
So short version, I'm really not sure between them, I like the feel of the m8 slightly more, but I like the slightly larger screen and battery of the z2, plus I'm slightly more inclined towards Sony over htc