Samsung had changed things a lot, and not for the better. For example, the volume keys are mapped to take photos rather than the zoom controller of previous iteration. Then there's the menu section. It's a jumble of settings strewn everywhere. Also, frustratingly, the phone maps the menu to the left of the menu and the back button to the right. This is opposite of stock Android. Almost all other phones have it the other way around. In addition, the location causes me to accidentally mash on the keys when in landscape mode.
However, the water proofing is a welcome though. I am also a fan of the multi window view for Samsung phones.
I like the Sony Xperia Z2, but the battery is it's Achilles heel. When on mobile Internet, even when charging, the phone battery drains rapidly.