only few processors are sensitive to the differences in timing between a modded PAL system and a genuine NTSC system. Most users won't notice and should not care about it.
I've actually found the NTSC modded PAL MD to be so far off spec its upset every processor I've tried, which is:-
DVDO Edge + XRGB3
DVDO Edge on its own
Optoma Themescene + XRGB3
Gefen VGA to DVI + XRGB3 and
XRGB Mini.
The effect was either a white line that cut across the picture every few seconds and/or stuttering during scrolling, except on the Optoma which wouldn't display the picture at all. I've not actually tried connecting my MD to a TV directly but I can't imagine the sorts of cheap upscalers in TV's as standard would be more forgiving. I believe with a CRT it would be perfectly fine though.
What about going the other way NTSC MD modded with a 50/60hz switch?
I think that would be fine, but I'm waiting to try this, the guy who does my mods has been tied up with other work lately.
a bit off topic. If you really mind the quality difference between component and RGB on a PS2, you can run a permament RGB connection into the Mini. You just need something to convert RGsB to RGBs for the 480p output - neither expensive nor complicated and it saves you swapping the cable.
Ah because PS2 uses sync on green if you set it to 480p + RGB? That's a good idea what converter would be needed? Perhaps an Extron RGB interface would do it? I've already got a AV distributor but that's a good solution for other users without such an esoteric setup.
Personally I would just get a Wii, which has worse component image quality than the Gamecube
Really is a lot worse though, but yes, Gamecube component cables are pretty rare now.
What's so bad about component quality on the PS2 that you need to do cable swapping?
Quality is just poor on component, it looks pretty ugly in PS1 games for instance, there's noise and moire patterns on parts of the image.