I don't mean to promote my own article, but:
"While trying out Wii games on my new Wii U, I noticed my set was reading the signal as 1080p. The game I tested appeared to look a bit sharper and more vibrant than I recalled. Making sure I wasn’t just falling for the excitement of a new console, I decided to compare some screens of games running on both the Wii and Wii U.
Wii:
Wii U:
Note my set reading the signal as 1080p.
Wii:
Wii U:
Note more vibrant colours and a vertical stretch to fill the black bar at the bottom.
Wii:
Wii U:
There you have it. I’m no tech wizard, but I do have a theory that HDMI may just inherently have higher quality output versus Component, but who knows? So whether or not the Wii U upscales Wii games is still up in the air, but I do know these screens objectively look better on Wii U."
http://www.consolexp.com/does-the-wii-u-upscale-after-all/
