I have both devices.
To be frank, both got pros and cons. Both is actually have similar (I repeat similar) specs, but not the same.
Physical size, both almost the same, N3 win in slightly bigger size (in mm calculation).
Internal storage comes in 16gb for Z2, whereby N3 in 32gb (at least here in SG, this is the internal storage size).
RAM is the same 3 gigs (both are smooth).
Battery 3200 for Z2, and 3100 for N3. But so far usage (my personal usage), Z2 has a better power management (both I use without power saving mode).
Camera, no need to say. Rear camera Z2 has a bigger megapixels (20 vs 13)
But Z2 loose on the front camera. So if you like to do selfie, it sucks
The sound to be frank Z2 is nicer in my opinion. A lot of my friends and relatives said sony xperia got a bad sound quality especially when plug in the earphone. But this Z2 is nice. I tested using the same earphone on my Z2 and N3, Z2 is much better.
Custom ROM, N3 (especially N9005) got more custom ROM compare to Z2 (maybe Z2 is still new device).
On the other side which Z2 will never win N3 (or note series) is the S-pen. If you like/need to use S-pen for your daily driver (like me), N3 is all the way win. To be frank, I need the S-pen (and all its features). That's why I also never use CM/AOSP base, even I know CM/AOSP is much faster compare to TW.
But when carrying Z2, I don't need to scare that my phone touch water on the rainy day. whereby N3, I need to be careful. So when I'm doin my outdoor activities/work, and I need to use to capture pictures, Z2 will be quite handy and useful at any conditions.
Z2 front and back are tempered glass. So have to be careful not to drop it, otherwise it will break. And better put the screen protector for both side (if you are quite careless in handling phone), to avoid scratches.
So in my opinion, both are good phones with its own pros and cons.
M8 ? G3?
