Depends on a lot of factors. Generally for PC, I believe you'd want RGB. A quick Google looks like 4:4:4 should be the same as RGB.
Make sure that other settings are equal, that one isn't using some extra saturation or other similar color "boosting". For instance, your display could be sending info telling that its a TV and the video options might be using modified color profiles.
What display do you have? Some support extended color specs, but color space is so screwed up (there's a lot of different standards) that you're going to almost certainly be screwing with color accuracy.
Also check things like Digital Vibrance (not sure what ATi calls their similar option).