John: If the signal is "S" all the way thru from start to finish, then yes it could improve it over regular composite. Of course if the signal is bad to start with, it won't make it better...
being that its a bigscreen and more noticable i would say it would be better through the s video,although im not for certain.I tried running things through the vcr with rca jacks,but the picture was worse,because the vcr must have a cheaply made tuner in it.Digital boxes should provide a top level picture.S video being better than regular cablevision wire.