Okay, after having played pretty much the most taxing tracks in the game which killed the Wii U's framerate (Sky Pirates track and all the ones with water like Panzer Dragoon), I can legit say I'm pretty impressed with the emulation!
Felt like a solid 30fps throughout and if there were drops, I didn't spot them at all.
At this point, I'd say XB1 is the definite version behind the PC
But to summarize all the versions:
1. PC - 60fps/high-resolution + added exclusive PC characters like Ryo
2. XB1 - Sub HD, most stable framerate with added Vsync
3. Xbox 360 - Sub HD, most sable framerate last gen on console but w/ tearing
4. Wii U - Lowest resolution of the bunch (game looks bad on a big screen TV), fairly stable framerate except with certain, CPU intensive tracks. Off-Screen play and ability to play on different screens
5. PS3 - Actually 720p but with lowest average framerate and a fair amount of screen tearing
I did get a kick out the fact that the Wii U version I own DOES load faster than the XB1 version due to running of a 128gb flash stick.