I have been trying to figure out why Wii U 480p looks so bad (not just in vWii). I assumed it was because Nintendo added a blur filter for whatever reason, but that hardly makes sense since the picture should still have even scanlines and some uniformity. Instead it looks distorted.
I downloaded Zero Mission because I heard the VC GBA games are great. Sure enough, it looks flawless and even has a pixel perfect mode (1440x960 in Wii U's 1080p mode and 960x640 in 720p mode). I captured a few screenshots of these and magnified many times they're still perfectly clean without any blurring, soft edges, distortions or artefacts.
Zero Mission at 480p on the other hand is a mess. The proportions are strangely off and even in pixel perfect mode the game is blurry. This actually makes no sense because GBA games should be a perfect 3x scale (720x480). On the gamepad it is this res and looks correct. On the main screen output, it's not. What I have noticed is that 480p mode (throughout all Wii U and vWii applications) uses one or more strange resolutions that conform to no standard. Neither 16:9 or 4:3 seem to fix this.
This might explain why back in vWii mode, I found it impossible to get evenly spaced artificial scanlines in 240p Suite's 480p mode and a SNES emulator, no matter the resolution settings. 720p and 1080p are non-integer scale so that causes typical unevenness. And 480p mode is spitting out a weird sub-480p res.
I'll post screenshots when I have a chance.