Just found this page in internet and looks very promising as my next car gadget

But i have a question regarding bluetooth connection.
My car - Toyota RAV4.3, GPS Unit: Roadrover D7009TR (with BT, with USB Host, WinCE 6.0)
What would be better option? Bluetooth or USB Connection??
If i will choose Bluetooth:
- what will happen if i will have my phone connected via BT to the unit? Can both devices work in the same time? Or one will be disconnected?
Cheers
proxonic