With USB + BT the only (IMHO) benefits for a phone-specific cradle would be to (1) power the phone (w/o the dangling cord) and (2) connecting to the external antennae for better signal. Since those have never been a problem for me going back to the days I had a BMW Motorola Startac (beam me up Scotty) in my early 740 and phones change form-factor every year I see no advantage.
My opinions are free - you'll get exactly what you pay for!
1998 Z3 2.8
2007 Rav4 V-6 AWD