Scart has it's plusses and minuses... It can carry composite video, (true) rgb and s-video. The trick is that the connector is always the same, but *not all* of the pins are always connected and thus not all the aforementioned signal types are actually carried (depends on the cable and of course the computer and display).
The best picture quality (which actually is comparable with vga) is rgb via scart. The signal is not compressed, only the sync is different compared to vga. I can assure you that for example my belowed A1200 produces a great picture even when hooked up to a modern lcd pojector (1920 x 1080) via scart directly from the A1200 rgb out. Qualitywise the possible signals carried via scart are (in descending order):
1. rgb
2. s-video
3. compos(h)ite
