head to head
Neither is simply harder - they are hard in different places. Grand Theft Auto V demands more reads; Mothergunship demands more variance.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.

Execution · Practiced Mastery
Bullet-hell dodging fed by a solvable gun-crafting system across random rooms.
Grand Theft Auto V leans Execution (Practiced Mastery); Mothergunship leans Execution (Practiced Mastery).
Mothergunship leans clearly harder on execution.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Mothergunship
Dodging bullet-hell rooms while jumping demands real twitch skill
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Mothergunship
Robots follow fixed firing scripts with no adaptation
Mothergunship leans clearly harder on variance.
Grand Theft Auto V
Some mission and lobby randomness.
Mothergunship
Randomised rooms and shop offers shape every run
Mothergunship leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
Mothergunship
Gun-crafting combinations are a solvable engineering puzzle
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.