I would recommend the Westin Osaka, from KIX you can take the train from KIX to Osaka Station (about 50minutes), then you can catch the shuttlebus to the hotel.

Not sure if you have been to Osaka before, but right next to the Westin is the Umeda Skybuilding, its a futuristic looking building and a sky deck. You can take the shuttlebus to Osaka station where there's shopping areas, or you can catch the subway and commuter rail lines at Osaka/Umeda Stations to explore the rest of Osaka.

The Kobe Sheraton is a bit from the station, not to mention its in Kobe about 30 minutes from Osaka Station and 1 1/2 hr from KIX.