I haven't stayed in any hotels in Seattle, but I can say that the train is the way to go between Seattle and Vancouver, so long as the rails are not blocked by mudslides, which happens occasionally during the rainy season. If that happens, then they will bus you up to Vancouver instead. Still not a bad way to travel as the buses are generally very comfortable.
If you take the train - make sure you book on the Cascades train. It starts in Oregon, as opposed to the one that runs all the way up the coast from Southern California. The Cascades has a much better on-time rating.
Oh, and if you can, splurge for the $15-25 upgrade to Business class, especially on the run up to Canada. In Vancouver, they let the Business Class disembark first, so you get through customs much faster this way. On the way back down to Seattle from Vancouver, you go through Customs on the train, right after crossing the border, so you don't get that perk.
If you have any questions about sightseeing in Seattle, let me know. It's a great city!