Welcome to mp3car. You seem to have stumbled upon the wrong forum, as this is typically about installing a PC into a Car (EG: CarPC).
Very few, if any people here use headunits anymore, so we put our audio (be it mp3, flac, or whatever format you desire) directly on the PC and play it from there.
You would probably have better luck asking these questions on an Car stereo forum, since they likely actually use stock headunits.
Oh, and no headunit is superior, so give it up, get a carpc, and problem solved. Carry all your media with you in the carpc and you don't have to worry about quality between your ipod and your stereo