difference between note 2 and latest models

i have been due an upgrade for some time, but stuck with the note 2 as it does exactly what i need
but it is getting on a bit and slowing down, if i was to upgrade to a note 4 or whatever is next coming out what would i lose? and what would be biggest gains?

I love the note2 battery life - and chargers pretty quick. this was wit hthe original battery, and then i bought a replacement (said genuine note 2 batt) a few months back to breathe some life back in to the phone.

i love the ability to airplay images and video to my samsung tv.
(and even to other models with the play2 app).
the screen size is good.
The screen is even good in sunlight when i increase the brigthness.
I like the ability to increase storage with the sd card slot, i hear some phones dont allow this now. Pictures do get backed up but i dont intend to download them everytime i want to view them, havign them on the phone is crucial.
I havent rooted the phone due to issues with GPS and maps on an older phone, as these are pretty important to me.

What have people been impressed with when upgrading and what have you missed?