This is very subjective and hard to answer. We loved the Norwegian Sky and as you can see above, keukamom didn't. We only used the indoor buffet in the mornings and pretty early but never had any seating troubles.
We also sailed the Zaandam and the Mercury and enjoyed both those ships as well.
One advantage to the Zaandam is the main pool is covered so if you like staying by the pool that would be an advantage. The pool is also fresh water.
Mercury has a small covered pool and Sky had no covered pool. Pools were salt water as well.
I just returned from AK on Holland America's ms Amsterdam. What a beautiful ship and I would definitely recommend it for AK! There are a lot of lounges and sitting areas which have gigantic windows to show the best views of the state. Also, we had to use a tender only once, and that was in Sitka.
Plus, the service on this ship was outstanding!