I asked this same question a few months ago; we spent our first 4th of July in WDW last month. We watched the MK fireworks on July 3rd, and Epcot's on July 4th. Epcot did the regular Illuminations show, which was followed by additional fireworks. Both shows were spectacular.
Obviously, being at BWV means Epcot, or even The Studios (which also has special fireworks) are easiest. I wouldn't say that MK's were any better than Epcot's, just different.