I did a little experiment last night to see what the differences between the stock regular composite cables and Mad Catz Universal S-Video/Composite video cable.
I have a
RCA 27v530T. All the TV settings I reset to there default settings, no tweaking was done to the tv's brightness or color settings.
I connected the regular out the box composite cable that comes with every gamecube to the yellow composite connector, turned on the cube with Resident Evil 4. The picture was dark, colors weren't bright and kind of mixed together, and the picture wasn't very sharp.
I unpluged the cable, and plugged in the Madcatz Universal S-Video cable and connected it to the GCN (restarted the cube and TV). The picture was much richer in color all the browns red's and every color stood out unlike before, the picture was much sharper; before I had to really try to read Leons racoon police departpent badge on his arm, with the s-video I could clearly see it/read it with out even trying. The picture was brighter and everything on the screen was much better.
The Differences between the two was like night and day, with the regular stock composites the picture was dark, colors didn't really pop out and bled together, picture wasn't very sharp. With the S-Video cable from madcatz was the complete opposite of the regular composites. I can still get a better picture if I fine tune my TV's settings. Now, not All tv's are the same and your results may vary from mine.