I prefer the fenced open viewing area near Casey's. It's where Disney used to have the FP+ folks. But you have to get there early for a spot there - like an hour early.
If you are planning on leaving after the fireworks, my 2nd fav spot is on Robo's Map in the middle of the road between Casey's and the Plaza in the green section. It's easy to turn and leave down the street from there. That area seemed to be good to get 30 minutes before the fireworks.
If I'm going to be staying after the fireworks, I'll choose a spot on either the Tomorrowland bridge side of the green area or the Adventureland side green area - both areas are good viewing. It all depends on which way I want to go after the fireworks if the park is open late.
Both of those areas got full 30-45 minutes before the fireworks. I usually get some popcorn and drink and relax while waiting.
In my experience all the prime viewing spots were taken 30 minutes prior so you may want to look for a spot just before then. And the bigger the group, the earlier you'll want to get a spot.
Because it's newer fireworks it is definitely more crowded even on days when you wouldn't think it would be.
Have fun!