We have been to Alaska 3 times. Never had a balcony. Twice we had an inside and once a window. I am usually up early roaming the decks for photos and lido for coffee.
As Dave said rail space is hard to find in Glacier bay. I try to spot a few of the out of the way spot before we get to the Bay. Also I do not tend to stay put.
We also try to book a cabin close to an aft deck. We prefer the aft section.
For us a balcony is no worth the price. However when we cruise the warmr waters to Mexico I usually get one.