I upgraded from iPhone 4S to Note 3. Here are my pros and cons (Purely based on my experience):

Pros:
1) BIG screen! (great for web surfing, viewing pics and vids.)
2) Feels very light even for such a big phone.
3) S Pen!
4) Flexibility of Android (almost limitless freedom to customise even without rooting)
5) NFC
6) Expandable memory

Cons:
1) KNOX. 
2) Samsung Bloatware
3) Camera UI all over the place and not very quick (e.g. it takes more steps on the Note 3 to take a panorama pic. and you can't take a vertical panorama pic on the Note 3)
4) Overall UI feel does not feel so well put together. (iOS is still that bit smoother and more cohesive)
5) Bugs I encountered with my phone like random restart and occasional "green screen" (just my bad luck I guess  )

Hope this helps