I don´t agree.I think the jaggies look more noticeable/accentuated with an HDMI signal, and I'm playing on an Asus 23" LED screen (Wii U looks fantastic), the games are "scaled" to match the 1080p, but they are still internally, 640 x 480. RGB/component makes Wii games look better.
Full digital is always the preferred signal.
The image for Wii games looks cleaner, sharper and the colors are better.
So yes, the image over HDMI is better.