head to head
Mario Kart 8 Deluxe asks more than Mario Kart 8, and the gap is reads.

Execution · Twitch Chaos
A kart racer where controlled chaos from random items tempers otherwise precise driving skill.

Execution · Twitch Chaos
A kart racer where item luck collides with optimized lines and builds.
Mario Kart 8 leans Execution (Twitch Chaos); Mario Kart 8 Deluxe leans Execution (Twitch Chaos).
Mario Kart 8 Deluxe leans a little harder on execution, though the gap is small.
Mario Kart 8
precise drifting and item timing matter
Mario Kart 8 Deluxe
Drift boosts, snaking, and item timing demand precision.
Mario Kart 8 Deluxe leans clearly harder on reads.
Mario Kart 8
minimal, mostly reacting not predicting
Mario Kart 8 Deluxe
Human racers bait and block items but mostly reactive.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Mario Kart 8
item boxes are heavily randomized
Mario Kart 8 Deluxe
Item distribution heavily randomized by position.
Mario Kart 8 Deluxe leans a little harder on optimization, though the gap is small.
Mario Kart 8
track lines and item strategy solvable
Mario Kart 8 Deluxe
Kart build, line, and shortcut knowledge define top times.
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.