head to head
Mario Kart 8 asks more than Subway Surfers, and the gap is optimization.

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

Execution · Twitch Chaos
An endless runner testing swipe reflexes against procedurally generated obstacle streams.
Mario Kart 8 leans Execution (Twitch Chaos); Subway Surfers 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 8
precise drifting and item timing matter
Subway Surfers
Swipe reaction speed at increasing pace is everything
Mario Kart 8 leans a little harder on reads, though the gap is small.
Mario Kart 8
minimal, mostly reacting not predicting
Subway Surfers
No opponent - just oncoming obstacles
Mario Kart 8 leans clearly harder on variance.
Mario Kart 8
item boxes are heavily randomized
Subway Surfers
Procedural track segments keep each run unseen ahead
Mario Kart 8 leans clearly harder on optimization.
Mario Kart 8
track lines and item strategy solvable
Subway Surfers
Powerup upgrades matter little beyond reflex play
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.