If I were visiting Boston for sightseeing, I'd choose the Seaport property over the Back Bay/Fenway location. The latter hotel really isn't in Back Bay. If you plan on going to several baseball games it has good access to Fenway Park and some nearby restaurants but not the typical historic venues that draw tourists to the city. You'll be taking public transportation (easily accessible) to Back Bay and other areas for that. The Seaport hotel is in an good location, plenty of new restaurants just outside the door, fairly easy public transportation access (about 10 minute walk), and you're closer to Faneuil Hall and the North End (30 minute walk along the waterfront). Personally, I prefer walking while sightseeing in Boston over riding the subway. The Seaport location is better situated to do that since the adventure begins just outside the door with an enjoyable walk to your final destination. The Fenway hotel doesn't have as much to offer a tourist outside the door - you'll need to spend a little more time, probably by subway, to get to typical Boston hotspots.