head to head
Neither is simply harder - they are hard in different places. A Way Out demands more reads; Grand Theft Auto: San Andreas demands more optimization.

Execution · Practiced Mastery
A co-op action-adventure where two players must synchronise execution and planning to break out and stay free.

Optimization · Practiced Mastery
A sprawling open-world crime epic with RPG-style character stats across a whole state.
A Way Out leans Execution (Practiced Mastery); Grand Theft Auto: San Andreas leans Optimization (Practiced Mastery).
A Way Out leans a little harder on execution, though the gap is small.
A Way Out
Timed escapes and combat require responsive, accurate inputs
Grand Theft Auto: San Andreas
Flying school and drive-bys need decent hands
A Way Out leans clearly harder on reads.
A Way Out
Co-op partner coordination requires some social prediction
Grand Theft Auto: San Andreas
Gang AI is scripted, never adaptive
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
A Way Out
Enemy patrols have scripted paths with some unpredictability
Grand Theft Auto: San Andreas
Territory wars and traffic add light randomness
Grand Theft Auto: San Andreas leans clearly harder on optimization.
A Way Out
Escape routes and combat approaches have learnable optimal lines
Grand Theft Auto: San Andreas
Stats, gym, weapon skill, and routes reward systematic 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.