It is absolutely an improvement in every conceivable way from F-Zero X. The driving feels much better and tighter, the tracks are much more interesting and longer, the environments look astonishing even to this day, all of it is nothing short of fantastic. I didn't even find it as hard as some people say it is, hell I'd say F-Zero X and Wipeout 2 are harder, but that's because it does feel very fair.
I won't attempt finishing the story missions though, damn are those indeed hard as shit.