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

Execution · Pure Mechanics
A swipe-em-up arcade game where slicing accuracy against random fruit spawns is the whole skill.

Execution · Twitch Chaos
An endless runner testing swipe reflexes against procedurally generated obstacle streams.
Fruit Ninja leans Execution (Pure Mechanics); Subway Surfers leans Execution (Twitch Chaos).
Fruit Ninja leans a little harder on execution, though the gap is small.
Fruit Ninja
Swipe accuracy and combo timing
Subway Surfers
Swipe reaction speed at increasing pace is everything
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Fruit Ninja
No opponent
Subway Surfers
No opponent - just oncoming obstacles
Subway Surfers leans a little harder on variance, though the gap is small.
Fruit Ninja
Random fruit and bomb spawns
Subway Surfers
Procedural track segments keep each run unseen ahead
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Fruit Ninja
Combo and crit systems are shallow but real
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.