Do you mean composite? HDMI is much clearer than composite. It is only slightly better than component.
composite: red yellow white
component: red green blue
And for the love of god don't buy an expensive HDMI cable unless you need it to last 50years in a warzone, or you get it free.
There is extremely little difference between a $10 1meter HDMI cable and $100 1meter HDMI cable. Things get a bit more complicated when you have lengths of cable over 5 or 10 meters, but that's unlikely.
I have noticed no difference between HDMI on my 360 and going to component, but when I put it to composite the picture, becomes terrible on an HDTV.