There is more to do in Seward. The boat rides here are exceptional and are the highlights for me. On our last trip there, we spent 3 days out on the water. We love the hike to Exit Glacier, seeing Seavey's Iditaride, Sealife museum. It is just a beautiful small town with so much to do. A hidden gem that most people miss who go right from ship to airport. We did not have a car when in Seward and it was not an issue.
There really isn't much to see in Anchorage. We ate some nice meals there and enjoyed the Ulu factory but otherwise - it is a city and not really a tourist destination.