My personal preference is Epcot.
We've done four NYE's there and this December will be our 5th.
Epcot has two illuminations shows, one early for those not staying till midnight, and the other starts at 11:30 pm or so. It's timed so that it ends just before the NYE fireworks display begins
The NYE fireworks are a lot higher in the sky with generally larger fireworks than is used for the standard illuminations show.
Last year it was in rain. Hopefully this year will be a lot nicer.
One piece of advice, true for illuminations as well as the midnight fireworks. See which way the wind is blowing and select a viewing spot that is upwind from the fireworks. If you get downwind and the smoke stays low, it'll block your view quite a bit.
Have a great time.
We're staying at BWV. Where will you be? Transportation after everything is done can really be slow. All the parks are emptying out a lot of people all at the same time. If you stay at an Epcot area resort, you can walk from Epcot or MGM back to your villa. Anywhere else and be prepared for lots of traffic.