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

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

Optimization · Practiced Mastery
A punishing Soviet off-road logging sim about dragging timber through near-impassable mud.
Grand Theft Auto V leans Execution (Practiced Mastery); MudRunner leans Optimization (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto V
Driving and shooting demand decent inputs.
MudRunner
Careful throttle, diff-lock and winch control matter constantly.
Grand Theft Auto V leans clearly harder on reads.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
MudRunner
No opponent of any kind.
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.
MudRunner
Deforming mud behaves unpredictably until mapped.
MudRunner leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
MudRunner
Fuel, load and route planning across the map is the core test.
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.