Carol'sDisney - everyone seems to agree that Conch Key and Sago Cay have very good TPV views; there are some who prefer the TPV in Boca Chica, and there are a few TPV rooms on the end of Big Pine Key, but there are not that many. I can't really help on what floor is the best, both of the TPV rooms we've had were on the third floor, which was a good level, I thought.
jkstewart1800 - the lagoon views from Boca Chica will look out towards the Contemporary, while the lagoon views in Big Pine look towards the Poly. Both are very nice, but I prefer the ones in Big Pine. That's only personal preference, however - many people like Boca!
mbcary -They both have the same food offerings, and you get the same CM assistance with dining reservations and activities bookings. The main difference between the two is location. The rooms in Sugar Loaf all look over the marina or the courtyard, there are none that look at the lagoon or theme park. In RPC, you may have a view of the MK, or the courtyard, or the themed pool and wedding pavilion.
RPC is in the main building, and you get to be an elevator ride away from the monorail, shopping and most of the restaurants. You get to hear the lobby pianist, or the band in the afternoon/evening from the lounge.
Sugar Loaf is located in an outer building; their lounge is a bit less quiet, can be a little more crowded, but it is closer to the outdoor amenities, like the marina and boat dock, courtyard pool.