That's a hard one. I really like the Star Wars show/fireworks at DHS. The original one was better, but the current one is still awesome. But MK fireworks are very sentimental for me. If you like Star Wars, do DHS. Otherwise, MK.
EDIT:
You might also look at what time stuff is showing. One time may work better. DHS tends to be earlier than MK.
If you are considering a dessert party, then absolutely Star Wars.