In my situation, HR20 and a 42" Samsung Plasma, There is zero difference betweem component and HDMI. I would get the Component first, if you are happy fine, if you want to try to improve it then check out monoprice.com. you can get a $5 HDMI cable. For sure DO NOT but the rediculous $100+ HDMI cables from the big guys.
I have both connected to my Optoma RD50 DLP 50-inch RPTV. I actually CAN tell a difference between the component and HDMI outputs, although it's very (VERY) small. There's better color saturation, and less "rainbow effect." I can see no difference as far as resolution goes.
But all HDTV and satellite receiver manuals say for the best quality picture use the HDMI output. I wonder why they state that. Maybe the difference can be seen on a scope, but not by the human eye!!
Generally, it's the analog-vs-digital discussion. There may be some installations where appliances, computers, electrical-fields, or large unshielded-speakers nearby might induce some interference on the component video cables. An HDMI at the same installation would probably be immune, since the D-A conversion is done in the tv.
where are you guys buying your hdmi cables? i bought a 15 ft cable for 25 bucks based on a recommendations from an avs forum member. i bought a second (6 ft) cable for 17 dollars from the same place. nice thick cables.....not anything junky!!!