Say, guys and gals in PAL Land.

What video output options do you use with your Xbox 360?

1. Composite [Single video Plug] (is this NTSC Only?)
2. S-Video (is this NTSC Only?)
3. SCART (Does this do HD or SD or both?)
4. Component [Three video Plugs]
5. VGA
6. HDMI
7. Other?

I would also love to hear your thoughts on whether or not it is worthwhile to even use a SCART Cable,
Assuming you got one for free,
and about your preferred cable to use to play Xbox 360 games in HD.

Consoles come with a scart adapter but it's not really scart. It's just composite and the audio which plus into a crappy adapter for those who don't have composite in. Scart is SD, and RGB Scart provides a far better picture on legacy TV's. Most won't be aware of that though, and will just use the supplied composite adapter.

S-Video, rarely used here. RGB Scart always gave a far better picture and was the European wide standard.

Oh, ok.
So, in PAL regions, the Xbox 360 comes with a Standard Def (low-quality) SCART Adapter.

I've been looking at this pinout:

Is that the "RGB SCART" version you are talking about?

If I put a SCART Connector on the back of the Xbox 360 case, and wire it up that way, will it be limited to high-quality SD, or will it also support 720p, 1080i and 1080p?

I'm designing a custom case, with prewired AV-Out ports on the back panel.
I've already figured out most of the Connectors that I'm gonna use:
VGA, Component HD, Digital Optical, Digital Coaxial, 3.5mm Stereo, RCA Stereo,
and a pass-through HDMI Connector for HDMI-Enabled 360's.

I want to make sure I don't leave out any vital HD connectors for you guys with PAL Consoles.

Yep that wiring is for an RGB Scart. It is much better quality than Composite video and S-Video, but not as good as Component video. RGB Scart only carries SD, not HD. It is basically the best quality SD connection in europe.

For me the case would be ideal if it had:
Composite, RGB Scart, Component Video, VGA, HDMI
Then for audio it had:
Phono, Coaxial, Optical

Nobody in europe really uses s-video (since rgb scart has superior image quality than s-video, and all dvd players etc come with rgb scart connections as standard)