The only dissadvantage of on line check in is the inability to request a specific room location at check-in. As of January the only requests avaliable were Handicap Accessible and Ground floor. (This may have changed).
This means you could be placed almost anywhere including Carousel. If you do standard check-in you can ask for them to show you general room location, and if you don't like it, request a room change on the spot.
Whatever you decide to do, have a great trip!