Both MK and MGM have unique fireworks displays on both the 3rd and 4th of July. We were at WDW 2 years ago for the 4th of July, and will back there again this year. MK does Fantasy in the Sky on 2 nights a year, July 3rd and 4th. MGM's fireworks are shown only once a year, on the 4th of July! Both fireworks are awesome! We will be back at MGM this 4th of July, watching fireworks and going to Fantasmic! We will do to MK on July 3rd! That way we get to see them both.
If you plan on seeing Fantasmic on the 4th of July then make an ARD for the Fantasmic Dinner package,.... if you can!
Good Luck with all your plans,