On my 1080p tv Component cables go shit when I use 1080p resolution (for example on my PS3).
Component cables are only good for 720p and 1080i.
Besides, HDMI is digital so that should be better anyways.
(Wikipedia it.)
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And I am thinking about getting the HDMiKey for the Wii. As it actually puts a 1080p/1080i/720p resolution if you set it up like that.