I played a tournament on Switch immediately followed by a tournament on Switch last night and some of the variances were interesting*:
> The track name shows up on Switch
... it has long since disappeared in the U version for some reason
> The results table is still shown better on the U version; once a race has finished the race results are shown and then the overall positions are shown, but the overall positions are not shown on the Switch version. Quite an odd omission
> The between-race text chat function runs for longer on the U version than the Switch version; on Switch you are sometimes cut out of the text chat before everyone has chosen their choice of track. The button to access the text chat has changed, too (A on the U, X on the Switch)
> The bump in graphic resolution on the Switch really is quite nice... and the shiny crown worn by the last race winner on the course selection screen is a cool touch!
The great thing is that the game feels the same on both versions; you shouldn't have any trouble adjusting from one version to the other.
*
Well, maybe not interesting... but I noticed them .