I have worked with tv systems, and stereos for many years. I have learned a lot about the different types of connections, components, and more.
While there are HDTV cables and connections designed to make your tv experience perfect, it really depends on your end result, and the equipment that you will be using.
The only difference between HDMI, and component cables is that HDMI can carry audio & video. Component cables only carry a video signal.
There is anotehr type of connection that isn’t really used on many of the current model tvs that are being sold. This connection is DVI. If you have a component with this type of connection, then you can purchase a DVI to HDMI adapter.
If you are simply connecting a tv to a HD box, then you can use a HDMI cable. On the other hand if you are going to connect your tv to a HD box, and a stereo system, then you will want to connect your tv to these components through the use of the stereo.
When you have a stereo system the sound is controlled completely by the receiver. If you use a HDMI cable in this same sequence, then you will resultingly acquire an echo from the tv speakers. The correct way to connect this setup is by using component cables.