I would look at your interests and budget and try to come away with the best, well-rounded trip.
Ketchikan: Ocean kayaking with Southeast Sea Kayaks. It was very easy and beautiful. We did the Orca Cove tour, which is in a very secluded place. They max out at 6 guests and we were lucky enough to get it so that it was just the 2 of us and the guide. Bald eagles flying all around us and you can paddle quietly right up to them when they are on the beach. Afterwards, they give you some great smoked salmon, fruit and cheese.
You can easily see town on your own. Just have an idea for where you want to go to save some time. We did Creek Street (of course) and the Salmon Hatchery & Totem Heritage Center (both of which are quite short)
1, We wanted to do some hiking here in the Tongass (temperate rain forest that stretches down through Ketchikan, Canada and into Washington/Oregon). After doing it, I'd say I totally underestimated the experience. Its an amazing environment ... it has no real soil, developing from the bedrock left in the wake of the glaciers, so 100 foot tall trees grow with very shallow roots. You get a real appreciation for the plantlife and the development of the forest. We lucked out and were there during berry season, which was a nice treat. [We were going to do the Guide's Choice Hike but went with the Rain Forest Discovery Walk because of a knee injury in the group and more hiking to come. The Walk is very very easy. Both are through the same company.]
2. Can't recommend enough some helicopter glacier flightseeing and landing. Expensive but very worthwhile. You get a far better understanding of the glaciers from this perspective. We opted for the 2 hour glacier trek, which was about 30 min of flying + 2 hours of hiking on the glacier. It was breathtaking and really not all that tiring because they take many breaks for pictures and to walk people 1-by-1 whenever you go up or down any incline. [I would have done Misty Fjords but decided I was only going to do 1 flight experience and far preferred this one.]
I can't speak to Sitka but the buzz is about Russian culture and wildlife viewing of otters, etc.
We are also not much for shopping. The best advise is to fill in gaps by shopping but to deal with excursions first. Ketchikan seemed to have the largest to offer with respect to galleries (at least the largest clustered easily together). Otherwise, most shops looked the same in most ports.