Isn't the video in the Neo Geo actually in digital form internally, and then converted internally to RGB (which is an analogue signal)? Technically you could say the source is the original digital signal (for any arcade system which is based on digital computer technology, which is all of them). So theoretically you would get the "best" (i.e., most accurate) output by modding the Neo to output in digital, and then sending that to a digital display (because even with RGB you get a slight loss in the signal when it goes through the cables, because it's analogue). But I guess the Neo was really designed to work with analogue RGB CRTs that arcades had at the time. Also, a lot of the LCDs/plasmas you get these days wouldn't have as good color reproduction as the high quality CRT TVs or PVMs had.
There is a huge misnomer that digital is superior to analog.
Keep in mind VGA and Component video are analog formats that can support 1080p video. They do not work with Bluray players due to HDCP encryption and not because they are inferior.
Your Neo Geo as well as just about every older game system outputs in 240p and at 15hz. CRT Televisions will interpret 240p as 480i, on a CRT Tv there no difference.
What makes PVM (and BVM) so great is that they are broadcast industry grade displays. As Broken said RGB is superior as the image starts as RGB at the source and gets encoded to Component, Composite, S-video or (Meh) RF, even if you have to mod the console to output to RGB.
Try running a Snes or a Genesis though composite video to a HDTV, the picture is horrible.
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