Sometimes. Sound quality in order from best to worst is physical media like CD's, direct connect like plugging your phone in via a cable (higher quality formats beat lesser lossy ones obviously), and last is over air like Bluetooth. I proved this to my gf by having her play a song or two over BT then had her plug in her phone and play the same songs - quite a noticeable improvement.
So, I prefer CDs for the sound quality but they are inconvenient to carry around in the car, so mostly I plug in my phone and play my music that way.