It won't really matter for playing music either way. I seriously doubt that the USB ports in the car are USB 3.0 ports. Having a USB 3.0 thumb drive plugged into a USB 3.0 port on a newer computer will let you read and write to the drive at higher sequential bandwidth speeds (in the 80-100MB/sec range), but even USB 2.0 has more than enough bandwidth to stream audio files with not problem.