The IC Tokyo Bay is located about equidistant between Tokyo and Shinagawa stations, both N'EX (Narita Express) stops. If you're intent on taking the N'EX, I would recommend the Tokyo stop as: 1) Not all the N'EXs stop at Shinagawa Station, but they do all stop at Tokyo Station; 2) From Narita, the N'EX arrives first at Tokyo Station and then about 10 minutes later at Shinagawa Station (if a stop).