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

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

Execution · Practiced Mastery
An arcade isometric shooter testing twitch execution and loadout mastery for score.
Grand Theft Auto V leans Execution (Practiced Mastery); Kill Knight leans Execution (Practiced Mastery).
Kill Knight leans clearly harder on execution.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Kill Knight
Ultra-fast isometric shooting and reload timing define mastery
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Kill Knight
Horror swarms follow fixed spawn logic
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto V
Some mission and lobby randomness.
Kill Knight
Arena waves vary slightly between attempts
Kill Knight leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
Kill Knight
Loadout synergy and scoring systems reward deep study
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.