The intermission tracks of MKW do add some additional content beyond the typical 8 cups/32 tracks but mainly they are just an extension of the base tracks and they don't feel much different. In terms of replay value, they add little. I'm already kind of bored of the content in MKW so I hope they announce DLC soon.
MKW needs some DLC of its own to compare. Hopefully they will bring in some crossover tracks and vehicles again. The F-Zero tracks in MK8D are among my favorites. The Animal Crossing track with seasons is great too.