Camera.

I heard this on a podcast a while back "You'll never look back and remember the screen/battery/etc jump from X -> X+1 and those changes all run together in the end but your pictures are only as good as the camera they were taken with".

It's for that reason (and because I like playing with new tech) that I upgrade yearly (upgrade program, I'm just perpetually paying a monthly fee for my phone). I'm well aware that this is "wasteful" or not the best financial decision for most people but it's a cost that I am happy to pay because upgrading and playing with the "new hotness" is fun for me. Also I always know I'm getting the best picture I could be getting (I'll never carry a dedicated camera so it's my phone or nothing).