I'm very much interested in the best side for the Hubbard Glacier viewing.
Well, I don't think you can see Hubbard Glacier from the ship (correct me if I am wrong), it is on the outskirts of Juneau. But there are other glaciers to see from the ship in Glacier Bay.
Unfortunately , there is no way to know which side is best until you get there. The captain usually turns the ship around so both sides get an equal view, but logically the best place is outside of your cabin so you can walk across the ship when he turns it.
You are always going to see more on deck than on your balcony - so in other words don't worry about that.
I have had balcony cabins on this iten on both sides of the ship(Mercury).
Either one was just fine. I usually pick the starbard side but my last was on the port and I enjoyed the views just as much.
As Paul said.....get out on an open deck to truly enjoy the splendor of the glaciers.
As mentioned below, the ship will rotate so 1/2 of the time the glacier will be viewable from your cabin. You can then go up on deck and view. Best views will be from the front of the ship as you're entering the bay however it could be chilly and crowded up at the bow.
Mendenhall glacier is the on the outskirts of Juneau.
We loved the Mercury and I'm sure you will as well.
We were on starboard on this same ship to Alaska when we sailed out of San Francisco and up the coast. If it's a round trip thru the Inside Passage you will see the same coastline coming and going. We really enjoyed this cruise. Alaska is awesome.