If you have one day I would say Universal. SIL did Uni a few months ago, and just needed a day to do all the HP still plus the backlot tour and a few rides and it sounded like enough time.
If you have 2-3 days I'd say Disney. We just did DL (came on here to post a trip report!), even though we had done WDW last April vaca. It's the same but different. DL is somehow easier to manage, you can jump between the parks and if you stay onsite you get Early Entry to DCA one day and DL the other (so helpful to fitting in mostly everything!). Plus DCA had Guardians of the Galaxy (slightly obsessed ).
"Every mother needs a wife." - Amy Poehler, Yes Please