You see Mario Kart 8 has a feature that Deluxe is lacking, and more than likely will never intergrate due to Nintendo's DMCA claim litterally everyone that used this feature:
This feature promoted the game all across the net, from the likes of waluigi just being weird to luigi's death stare reaching everyone and their mothers.
Now keep in mind they didn't completely remove playbacks but they did remove the editing power it had, and the ability to upload and share them, now we are just downgraded to facebook sharing of screenshots.
This feature was purely made to promote the old mario kart 8 for WiiU to try to get the youtubers in on it but Nintendo outlashed in desperation for ad revenue from said feature placing strikes and forcing everyone to join their partnership program if they didn't want strikes in which they were prohibited from giving any negative criticism of Nintendo and their decisions. Burning the bridges of content creators across the board.
Those whom did speak out in a negative fashion were kicked out from the partnership program and often got a DMCA strike against them. Alas this lost feature is very much unlikely to ever return, which would have been great in their real working battle mode not that excuse of one in old MK8.
Deluxe's battle mode actually is massively more enjoyable and a few of the levels look much higher detail than some of the MK8 courses which got a graphical upgrade in the bump map, cube map, and tessellation. Along with a higher anti-aliasing, & framerate surprisingly.
But the shadows actually look worse some how, much far worse actually. Everything else looks about 10% better than the WiiU version but the shadows stand out at being much far worse very pixellated in comparison to the already bleh looking WiiU shadows they managed to look worse, which I can understand to some small degree.
But I am thinking they thought none of us would notice or knew just didn't care because everything else looks better slightly. They even cleaned up and reorganized the character select screen. I have to say I love this upgraded version but this is what it should have been all along, but the shadows....