With new fireworks shows at each park debuting this week, I'm not sure I'd be ready to make that call right now! I'd likely book the Park Passes for Magic Kingdom (since it is more likely to sell out), but keep my eyes open for what each park is doing in addition to the normal fireworks. We have done both multiple times over the years and even both in one night (at times both parks have done an early and a late show on NYE). We will be there again this year, but are waiting for more feedback on the new shows as well as seeing what NYE things are planned.