We haven't gone yet but I think HS might be a half, or at least not full, day park for us. We are not Star Wars fans at all and our 6yr old daughter is not into thrill rides. We will probably do the shows, the Toy Story area, lunch and that's it. Again, we've never been so that's just "the plan" for now.
On the other hand - I know we can spend a full day at AK. We loves animals and plan on doing all the walking trails, and maybe even the safari ride twice (once in morning and then just before leaving).
Guess it just depends what your interests are. We are planning two full days at MK too. One day for Epcot.