I think Giuliano is your man, he's running 800X600 LVDS off his Commell LV-671 board.
If you're using short cables between your video card and monitor I doubt that there would be any differance in quality, but if you plan on mounting your computer in the trunk you'll have an advantage using LVDS.
The following is vague information from my memory when I was thinking about LVDS.
The VIA board, was that "real" LVDS or some wierd VIA LVDS version ?
Unfortunatley LVDS isn't just "LVDS", you have 18-bit, 24-bit, so you'll need to match a monitor to your output.
Most videocards do only standard resolution on the LVDS output, 800X600, 1024X768 and so on... if you're lucky you might be able to hack the video BIOS, if not... you're screwed
I gave up on the LVDS idea for three reasons:
1. Seems impossible to find a good 7" screen (reolution/brightness).
2. I'll mount the VGA controller and video card very close to eachother <4"
3. The VGA controller I got my hands on is soooo cool