Audio Quality with BT vs. Dock Connector iPhone

Hello all,
Just purchased a Mazda5 (awesome car) with Blue Tooth integration. Besides the normal telephone use of BT, the car recognizes the iPod music with it D2DP integration so from the steering wheel I can change tracks like I can from the iPhone wirelessly. Pretty cool. Mazda also offers as an optional iPod integration cable to the car stereo to use the steering wheel controls through the dock connector as well. I imaging this option would be necessary for a user with an ipod without BT but my question is would I gain any audio quality improvements using the dock connector vs. the BT? Im familiar with the dock connector to the ipod to the car stereo from my previous car so I know how fast it can respond to track changes. The BT as a footnote does have a slight delay when changing tracks. I guess to be expected. The audio using BT does sound good but was wondering if with the dock connector it will sounds even better. I know Im in a car and with road noise the music will degrade but I a fuss nut always wanting the best... Pitty my poor wife...
Thanks everyone.
Thanks!
27" iMac 2.93 GHz Mac OS X (10.6.6) Too many macs old and new to list...