Note 10.1 wins
I don't have a Z2 tablet but I have a Z1 phone, Note 3 and this Note 10.1
The thing I don't like about the Z1 was the lack of hardware buttons.
I don't like how part of the screen is wasted to provide these buttons on the Z1 as well as other Android tablets I've owned like Nexus 7, Asus TF101, TF201, TF300, TF700, Padfone Infinity.
Having gone from Dell Streak 5 to Note 1, Note 2, Note 8, Note 3, and Note 10.1 I feel kind of lost sometimes without the hardware buttons.
I feel like Samsung got it right, and Google Nexus and all the onscreen button camp got it wrong.
I even prefer the back button on the right as it has better ergonomics being directly under my right thumb as a right hander when using devices 2 handed.
And then there is the S-pen and Sketchbook Pro that puts the Note tablet on a different level.
If I was buying on looks and form, it would be Z2 looking pretty.
If I needed to use it with function over form, Note 10.1 wins easily.