S-video is "better" than a standard composite input. S-video splits the Chromiance and Luminance channels before transmission down the line, where composite (RCA) systems transmit all the data down a single coax.
Having said this, I haven't seen any out of the box solutions which include an S-video input.
The best system to drive any LCD is with an LVDS digital drive such as PanelLink but this can work out to be costly.
The best of the rest is the standard sVGA output with RED GREEN BLUE with either seperate Horizontal and vertical syncs or composite sync on green. but again panels with this kind of A-D decoder card built in are expensive.
I am personally a beleiver in using what you can lay your hands on easily and an NTSC display will give you the best "bang per Buck"
Hope this helps
System under development (Just need to fit to car).
10" DTSN flat screen with Microtouch touch overlay, 233Mhz Pentium MMX on a PICMG single slot proc card, 10 slot passive backplane (3 PCI 7 ISA), Custom Chassis, HARD Mounted HDD 6GB, Rand McNally GPS, SB Live 1024 Sound Card, Custom AC PSU, Jump it 300W Inverter, old ISA RS422/232/485 card, WinME:-(, WinAmp, AutoRoute 2001.