Whether it is worth it to upgrade is something everyone must decide for themselves. What I can share are my experiences. I've sailed to Alaska 3 times (1 w/Princess; 2 w/Disney; twice with a balcony and once with an outside cabin - we can't do inside, we'd sleep the whole cruise away!) When we had a balcony, we did use it more than we have on other cruises (Caribbean, Hawaii, etc.) It was nice to have a place that we could listen to the naturalist on the tv (and be able to hear it) and duck into the room if we got chilly and have easy access to a bathroom, room service, additional clothing, etc. But we also spent time in the public areas. When we didn't have a balcony, we spent a lot of time in Cove Café and the open decks. On Tracy Arm day I wouldn't attempt to be in Cove Café or trying to find a spot in a crowded area. We had plenty of room along the sides of decks 4 and 9 that we got to see everything and could come and go as we pleased. It was never very crowded there and we could easily go from port to starboard and back again. In fact on Tracy Arm day when we had a balcony, we still spent most of the time out on deck 4. Got to mix and mingle, see what other people were pointing out as far as wildlife and the characters and the hot cocoa cart would come around to you!
Either decision you make will be the right one.