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.

Optimization · Practiced Mastery
A sprawling open-world crime epic with RPG-style character stats across a whole state.

Optimization · Practiced Mastery
Methodically mapping a hostile station where knowledge and routing beat reflexes.
Grand Theft Auto: San Andreas leans Optimization (Practiced Mastery); System Shock leans Optimization (Practiced Mastery).
System Shock leans a little harder on execution, though the gap is small.
Grand Theft Auto: San Andreas
Flying school and drive-bys need decent hands
System Shock
Combat and cyberspace ask competent but dated reflexes
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto: San Andreas
Gang AI is scripted, never adaptive
System Shock
SHODAN's threats are scripted, not an adapting mind
System Shock leans a little harder on variance, though the gap is small.
Grand Theft Auto: San Andreas
Territory wars and traffic add light randomness
System Shock
Citadel's layout and logs are hidden until uncovered
System Shock leans a little harder on optimization, though the gap is small.
Grand Theft Auto: San Andreas
Stats, gym, weapon skill, and routes reward systematic play
System Shock
Inventory, routing and station knowledge solve the game
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.