I agree with booking a balcony. Sitting on the balcony while cruising the Inside Passage and seeing the beautiful tree covered mountains is one that I will never forget.
If you are cruising Glacier Bay I suggest booking a port side balcony cabin. The glaciers will be on the port side of the ship as you enter Glacier Bay. The ship takes longer to go into the bay and is closer then it is when it goes out.
If your budget is stretched I do agree with Cruise Planner and book an outside and go up on deck for the views and save your money for, at least, one big excursion. Flightseeing, helicopter trip to a glacier, dog sledding on the glacier are all excursions that aren't cheap but ones you will never forget.
If your budget allows it then definitely book a balcony and the big excursion.