If you use HD rated component cables (not cheap $25 standard def cables) on a calibrated input (where the brightness, contrast, color have been properly adjusted) you will not see any difference between the HDMI feed and the component feed. .You can not get 1080p signal going thru component connection, so you can not really compare. This is not true. Only Sony BluRay players have this defect. 1080p comes out great with component cables from non-sony equipment. Other than this I agree with everything AM wrote. Since HDMI carries both video and audio and is cheaper than HD rated component cables - it is the preferred way to hook up your gear.
If you're going to buy some cables, go with HDMI because they're no more expensive (if you know where to get them) and are at least as good as component video cables. That said, if you already have component video cables then don't go out of your way to buy an HDMI cable unless you have a surround sound system.
your cable box is not sending a 1080p signal, but it is sending a digital signal, there fore by basic common sense a digital cable (HDMI) will look betterbut not just any hdmi cable, a hdmi cable that is actually speed rated to meet the optimization standards of your tv. A 1080p tv is still using 2million pixels to show you the 1 million pixel resolution signal(1080i), so using a cable that is 1080p speed capable will give you a nice picture. Satellite will soon have true 1080p channels.but cable company is limited by bandwith, and can barely handle 1080i (don't ever get advice on hdmi form your cable company-they know nothing, they are coax orientated). Long story short, you probably wont notice a difference on cable tv. So just keep using your component cables. If you switch to satellite, then you would benefit from hdmi cables.
I've done many live customer demonstrations of HDMI cables versus Component and Composite Videos cables. In those demos I've used the different cable types between the same HDTV and Blue Ray sources to minimize differences only to the cables. Without a doubt, there IS a slight AND noticeable difference in picture quality with a HDMI cable that most people can see with their own two eyes. This was true for both 1080p and 720p HDTVs. There are more significant advantages to a HDMI cable other than picture quality. A HDMI cable is more convenient: one cable carries both audio and video signals. A 1.3a HDMI cable can help to keep voice video synchronized over the cable. A HDMI cable can carry superior digital audio signals. HDMI cables enable control of attached Home Electronic Equipment via the TV's remote control (HDMI-CEC aka Viera Link, Bravia Sync, AnyNet, etc). HDMI cables can carry movies at 24p frame rates for smooth motion presentation: I do not know of a HDTV that can do this with Component Video cables.
Yes, i don't think that component can support 1080P. Also component's quality is worse, the price is about the same, and component requires A LOT more cables. You need the component's AND another seperate sound cable (such as an optical, or the red and white cables) HDMI can also support Dolby TrueHD, and DTS-HD Master Audio while component can't
