Could you go on web-sites like tripadvisor, and look at lots of photos of whale watching at the different destinations..
Remember, that most of the good photos might have been taken with some real high-power quality zoom lenses.
We have been to Hawaii in the Spring (no whale watching), and Alaska in the Spring.
We were on Kauai, and while I have heard reports of seeing whales right from shore during seasn, and good whale watching, I am not sure.
We went whale watching out of Juneau (on the Scania)
This is in Auke Bay.
In our one experience, the boat was quite some distance from the whales. (I def. think he could have moved us a bit closer)
We saw a mother and a baby/juvenile, active in the water.
A couple of other whales.. one breached!!! But I was on one side of the boat and didn't really catch all of it. (should have been up on top with 360'!!!)
And we saw a couple of whales that were feeding close to the shore, going for tiny fish that must tend to follow the shore line.
These were the ones that we just happened to be closer too, by chance.
They were not working together to bubble-net... but were going under, blowing clouds of bubbles, and then scooping up the fish. But, without really breaching. Just surfacing.
If your huge priority is whale watching, I am not sure which might be best.
But, if you have been to Hawaii, and not Alaska, I tend to say 'experience Alaska'.
Happy planning!