You're question is so subjective. Others will have different opinions.
IMHO the best pool is SAB at the BCV hands down. The best location is the BWV followed very closely by the BCV due to the walking distance proximity to EPCOT and MGM.
Actually, there is an unambiguous "correct" answer to this, but it is not probably what the question intended. By far, the best studios are at Hilton Head. They are the largest and are set up somewhat differently than the other resort studios.