head to head
Neither is simply harder - they are hard in different places. A Story About My Uncle demands more execution; Grand Theft Auto: San Andreas demands more optimization.

Execution · Practiced Mastery
A non-violent platformer testing grappling-swing timing through fixed first-person courses.

Optimization · Practiced Mastery
A sprawling open-world crime epic with RPG-style character stats across a whole state.
A Story About My Uncle leans Execution (Practiced Mastery); Grand Theft Auto: San Andreas leans Optimization (Practiced Mastery).
A Story About My Uncle leans clearly harder on execution.
A Story About My Uncle
Grappling-hook swings demand momentum timing and aim
Grand Theft Auto: San Andreas
Flying school and drive-bys need decent hands
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
A Story About My Uncle
No opponents exist at all
Grand Theft Auto: San Andreas
Gang AI is scripted, never adaptive
Grand Theft Auto: San Andreas leans a little harder on variance, though the gap is small.
A Story About My Uncle
Course layouts are fixed and visible
Grand Theft Auto: San Andreas
Territory wars and traffic add light randomness
Grand Theft Auto: San Andreas leans clearly harder on optimization.
A Story About My Uncle
Finding efficient swing lines through each cavern
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.