I concur. They are probably best viewed in front of the castle. A close second would be around the lake (facing the castle). Of course, you'd have to deal with the Fantasmic crowd too (unless you want to watch both).
You'll also need to camp out at least an hour before hand. We got lucky last time and found a spot to stand in the area in front of the castle about 20 minutes to show time.
The fireworks are awesome, especially with the choreographed music,