We have been to both parks, but most recently was a visit to SW. As a matter of fact, we spent 2 days there and loved it. AK is ok, and there are some amazing and beautiful things to see, but, imho, nothing compares the feeding those dolphins. We spent 9 days "doing" Orlando last spring and one of the things my girls (then 9, 11, 15) still talk alot about are those dolphins. When we return in a couple of years, we will not only return to SW, but will probably go to Discovery Cove as well.
In addition to all that, I think AK is way more expensive, the crowds are huge like at all Disney parks and as another poster said, it is HOT. Again, just my opinon so no flaming, we took the drive to Busch Gardens rather than going to AK, and would do it again.
Whichever you choose, just make sure you plan well so your day will be all that you expect it to be.