Against all odds, the difference is significant and immediately apparent.
Super Smash Bros. Ultimate is now out, and while the game undeniably seems to take upon the (extremely solid) base of the Wii U game, it builds on it. A lot. In fact, one of the easiest ways to see just how much additional work was put into Ultimate over For Wii U is to compare the visuals of both, side by side, and see just how much added technical and artistic detail there is in the former relative to the latter.
A brand new video by YouTube user ElAnalistaDeBits does just that. It takes stages and characters that are common across both games (which is most of them), and plays them side by side, and you can see just how massive the differences are between the two games. The lighting and textures in Ultimate seem to be a generation apart compared to For Wii U.
That said, on the resolution and framerate front, at least, both games are evenly matched—Smash 4 ran at 1080p and 60fps, as does Smash Ultimate, albeit Ultimate does look far better while doing so.
You can check out the video below. If you haven’t picked up Ultimate already, you might want to do so now—all the cool kids, it seems, are doing it.