I don't think I could play that game on the 3DS. It already feels like it's being held back by the Wii's low resolution (though I suppose the poly count and textures aren't that great either), that playing on a 3DS screen sounds like a nightmare. But then I've never seen it actually running on a 3DS screen, so it might look better than I imagine. I'm not opposed to playing games on my 3DS mind you, just I prefer games that are designed around the screen, rather than games that are downgraded to port to it. But then I don't really have a lot of opportunity to play handheld games on the go, so if I'm playing a game from the comfort of my home, I'll pick the version that looks/plays better. People who travel a lot, or who can play games on their commute might have different priorities.
I need to get back into Xenoblade though. I was enjoying what I played of it (though I'm not far), but I no longer have access to a Wii Classic controller, and for some dumbass reason none of the Wii U control options are available when playing Wii games. So my only choice to continue playing is to play with a Wii remote, or buy a Wii Classic controller that will only ever be used for this one game. That has killed my drive to play further.