head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is reads, and it is a single point.

Execution · Twitch Chaos
N64 couch classic where blue shells and shortcuts decide friendships.

Execution · Twitch Chaos
Arcade stock-car driving where random power-ups keep races scrambled.
Mario Kart 64 leans Execution (Twitch Chaos); NASCAR Rumble leans Execution (Twitch Chaos).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Mario Kart 64
Mini-turbo snaking and shortcut execution
NASCAR Rumble
Arcade handling at speed still rewards clean driving
Mario Kart 64 leans a little harder on reads, though the gap is small.
Mario Kart 64
Couch rivals bait shells and fakes
NASCAR Rumble
Split-screen rivals can be baited with items
Mario Kart 64 leans a little harder on variance, though the gap is small.
Mario Kart 64
Item draws swing every race
NASCAR Rumble
Power-up pickups scramble race outcomes constantly
Mario Kart 64 leans a little harder on optimization, though the gap is small.
Mario Kart 64
Shortcut and line knowledge is fully mapped
NASCAR Rumble
Track shortcuts and item timing are learnable edges
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.