We've sailed both HAL and NCL to Alaska and yes, HAL's a bit nicer but we loved NCL and the freestyle freedom. I would not hesitate to sail NCL again in Alaska.
Glacier bay's a must IMHO. Hubbard's awsome....GB's more awsome.
I agree on the White Pass train. Also in Juneu do a whalewatch trip and also get yourself to the Mendenhall glacier.
Regarding a balcony or not....you'll get totally differing opinions on this so have to know yourselves and your budget. I feel a balcony's a must in Alaska for me. I'd rather spend the extra money on a balcony over say an expensive helicopter flight landing on a glacier. Glacier trip is great of course for an hour or 2. A balcony is all the time.
If you like solitude and kicking back a balcony's great. If you want to be out and about in clubs and casinos then inside will be ok. In other words....if you only will use the cabin for sleep and dressing no need for a balcony but if like me you love kicking back and nature watching....balcony's a must.