HDMI is 100% digital, so no, a $100 cable should not be better than a $25 cable as far as video quality. However, the more expensive cables should/can provide a more secure connection.
Video quality will be best with HDMI, next comes component, then S-Video then composite (RCA). HDMI carries up to 8 channels of digital audio (more to come) but I don't know of any TV that can do anything with more than 2 channels. This partially defeats the purpose of HDMI (single cable for audio/video), unless you have an HDMI switching receiver (newest models) so you can send multiple HDMI sources with multichannel audio to your receiver then send a single HDMI cable to your TV and mute the voulume on the TV, preferring the reciever/surround sound.
I just finished completing a new home theater so this is all fresh
