S-video, composite and component should all give a better picture than a standard RF connection. The RF connection requires an additional modulation to send the signal to the TV as channel 3 or 4. Have you mixed the terms "composite" and "component"? Composite is a single run of cable with RCA terminations. Component is a three cable RGB with RCA terminations. Is the box HD? If so, you must use the RGB to get the HD signal. S-video cannot pass an HD signal.
Digital cable set top box connections
A guy I work with just had digital cable installed and although the T.V. has component and S-video connections the cable guy installed it with the digital RF cable from the wall into the box and another RF cable from the box to the T.V. The box doesn't even have S-video or component outputs, only an RF and a single composite. The question I have is this; since the signal out of the wall is digital is the output RF also digital? If so is this the best possible connection? The cable company does offer a box with an S-video output but would this be a better connection? I've always known that S-video and component are much better than RF but is this true with digital also? Should he get the S-video box? Thanks in advance for your help.