Hopefully this might help clarify the S-Video Cable Query- There are two kinds... one display's full color and the other black and white, in construction they are built differently and that;s why there is a difference; To learn more google the darn thing...
As for the PowerBook/iBook video on a Television PowerBooks are FANTASTIC... The resolution on these doesn't matter because PowerBooks, are capabe of not only "Mirroring" but also "Dual Display" support, and your PowerBook will do all the thinking for you when you "Cmd-0" and go fullscreen; However for the iBook, you will have to "Mirror", although the iBook's Resolution will be really crappy, the Television will remain Television... or get some Third-Party hacks; To learn more google the darn thing...
Note* At least on the PowerBook you have several differing Video Resolutions for the televsion from <500x"X" to >1000x"X" (Okay I don't know for sure but there are options... Try it It's fun)
CHECK YOUR SPECIFICATIONS AND KNOW WHAT CABLE IS BEST, OR IF EVEN SUPPORTED BY YOUR COMPUTER MODEL.