The EPCOT dessert party is my favorite hands down.
I have done the MK x3, EPCOT x2 and Star Wars x3.
What I like best about EPCOT is the area has seats and you stay seated there to watch the show. Plus there is a bar! DH and I are more savory people and EPCOT has great savory options. A couple of sweets for us and that's it. We can drink our money's worth, as drinks at WDW are so expensive.
StarWars parties; The reason we do not like it as much as you are not seated in the same area that the show is. Our 1st party there were no seats, just tables. We were in the same area as the show.
2-3rd times we went, there were tables inside (A/C was wonderful) and then we were moved to our viewing spot. You could take your drink and a plate with your, but there was no place to put them. The full bar is awesome and the savory items are really good.
MK: We have done the parties for the private location only. The desserts were just a bonus. DH really does not like MK crowds for the fireworks, so the only way I can get him there is to book a dessert party. Do we get our money's worth, no. There is no bar. The savory items, I hear are better now, but when we went they were just ok.