AK for me.
Right now, I feel like USF is the worst park of the Uni/Disney group by a long shot. It has one great ride in The Mummy, one great classic in ET and then a bunch of middling to bad rides including one that is in contention for worst ride ever with F&F. The food is also kind of bad and the park itself just seems to lack any real charm.
On the positive side, it does have one of the best themed areas ever done in Diagon but the ride itself is a real let down.
AK on the other hand is amazing as an actual park. It has great food, amazing ambiance, theming is top notch outside of one section of one area and while it is most certainly lacking the number of rides it needs, what it does have is generally good and, in some cases, great with Safari, FoP, and Everest all being up there.
Both parks close too early so I'd call that a push.
Bottom line for me is Uni needs to badly refresh and revitalize USF while Disney needs to update a few rides as well as increase capacity at AK, hopefully all those things happen in the coming years as I would love a great USF and AK to go visit.