I did the 9pm show during spring break when it was extremely crowded. We did the dessert box, priority seating and LOVED IT

I know it is a lot of money ($118 for 2 of us), but it was worth EVERY penny! All we had to do was pick up our tickets at guest relations earlier in the day, check in at (or after) 7 pm (guests are seated in order of checking in), and go to our seats at 830. It was great, no sitting on the cold ground, drinking hot chocolate and bottled water (they also have tea and coffee I think), and snacking on our delicious snack box which includes cheese, crackers, grapes, an edible sugar spoon. and a variety of desserts.
My only recommendation is to have a very light dinner. We had a very filling dinner at Ariel's at 6pm and didn't make it back to check-in until 745 (and still had a great view!). Anyway, we couldn't eat much of what was in the box, so we took it back to our hotel and snacked on it the rest of trip! Oh, and the service was fabulous!
Also, you get to stay in your seats and watch the fireworks if you do the early seating! Cool!!
I haven't seen the WDW version, but I really can not imagine how it could be better because of where they have it in MGM. The raft and boat parts are truly spectacular and not to be missed IMO. Whatever you decide, have a wonderful time!
And PS. I've been to both parks now and have decided that DL is much better

it is easier to navigate and the theming on the rides seems much more elaborate!! (no offense....I still LOVE WDW!!)