I was on the Evening Whale Watch in Juneau and it was WONDERFUL. We saw about 4 or 5 whales and sat there for about 30 minutes just watching them surface and go back down. They weren't jumping out of the water or anything, but it was still VERY cool. Then we moved on and found some seals basking on a buoy. We were even lucky enough to see a brown bear on the coastline. The nice thing with it being in the evening is you get to do other excursions during the day if you want.
Any of the whale watchings will have opportunites for great sightings. I prefer Orca Enterprises- have gone with them 4 trips. Your sightings will be humpbacks with orcas only coming in every 5-10 days, if that makes a difference?? Orcas are best seen out of trips from Victoria BC or Friday Harbor Wa.