I actually did some moer side by side tests now that I have my whole GC library ripped. And what do you know sometimes there is this color bleeding and green blur like mentioned in that other topic. Sometimes there isn't. All this done with HDMI.
So yeah I guess it works. But even when it does look good, it doesn't look anything better than using component on a wii, more like the same. But yeah that is if the wiiu wants to play nice.
The whole point of using the wiiu was because of the hdmi cable. I'm not sure that tv's in the future will still support Component. So while I could connect component (official nintendo ones) to my wiiu it would beat the purpose.
Also I came to my own conclusion that it's just way more handy to use my wii over the wiiu when playing gamecube games:
-No need for the longer boot up of wiiu and then going to vwii (even with a forwarder this is long).
-No need for attaching the Gamecube adapter to use GC controllers. (less crap everywhere, including the wii being smaller)
-Wii is more silent.
-The support of official GC memory cards.
-The actual functioning of gamecube controllers in supported wii games (I know there are some fixes by using a different loader for those specific games, but that's just more fumbeling to boor a few games.)
-Actual fullscreen no black bars on top and bottom in some games, no fumbeling needed to fix that.
And yeah since the image when the wiiu plays nicely is practically the same as the wii using official component cables I just don't see the point in using the wiiu. For now it's back in storage. And if I ever get a new tv that doesn't support component cables I will either replace it with my wiiu or get a decent powered component to hdmi convertor (no wii to hdmi dongle crap).
Also to all the people that didn't see a difference. Like I found out it's more clear in one game than the other. And it would be more clear to you if you can run them at the same time like I did. Also I took the advise of configuring my tv to see if I got better results. It didn't help much. If the wiiu decided to display bright collors or bleeding green it didn't matter how much fumbeling I did.
If you still think it's just me or my tv read this conversation explaining the exact same problem:
https://shmups.system11.org/viewtopic.php?t=58155