head to head
Neither is simply harder - they are hard in different places. Mario Kart 64 demands more reads; S.T.A.L.K.E.R. 2: Heart of Chornobyl demands more optimization.

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

Execution · Twitch Chaos
An open-world survival shooter set in a hostile irradiated Zone full of anomalies and scarce supplies.
Mario Kart 64 leans Execution (Twitch Chaos); S.T.A.L.K.E.R. 2: Heart of Chornobyl 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
S.T.A.L.K.E.R. 2: Heart of Chornobyl
Lethal gunfights with recoil, bleed, and ballistics punish sloppy aim
Mario Kart 64 leans clearly harder on reads.
Mario Kart 64
Couch rivals bait shells and fakes
S.T.A.L.K.E.R. 2: Heart of Chornobyl
A-Life NPCs roam but never model the player adaptively
S.T.A.L.K.E.R. 2: Heart of Chornobyl leans a little harder on variance, though the gap is small.
Mario Kart 64
Item draws swing every race
S.T.A.L.K.E.R. 2: Heart of Chornobyl
Anomalies, emissions, stash rolls, and unknown Zone layouts hide information
S.T.A.L.K.E.R. 2: Heart of Chornobyl leans clearly harder on optimization.
Mario Kart 64
Shortcut and line knowledge is fully mapped
S.T.A.L.K.E.R. 2: Heart of Chornobyl
Artifact hunting, gear upkeep economy, and routing through the Zone
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.