head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

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

Optimization · Practiced Mastery
A Marvel team brawler where picking the right hero combos and fusions does the winning.
Grand Theft Auto: San Andreas leans Optimization (Practiced Mastery); Marvel Ultimate Alliance 2 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: San Andreas
Flying school and drive-bys need decent hands
Marvel Ultimate Alliance 2
Fusion timing and brawling are accessible.
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
Marvel Ultimate Alliance 2
Fully scripted PvE encounters.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto: San Andreas
Territory wars and traffic add light randomness
Marvel Ultimate Alliance 2
Small randomness in boosts and drops.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Grand Theft Auto: San Andreas
Stats, gym, weapon skill, and routes reward systematic play
Marvel Ultimate Alliance 2
Roster synergy and fusion choices are the real lever.
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.