head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is variance, and it is a single point.

Execution · Practiced Mastery
A massive open-world sandbox built around grappling-hook and parachute chaos.

Optimization · Practiced Mastery
Revenge-driven open-worlder dismantling a sixties crime empire district by district.
Just Cause 2 leans Execution (Practiced Mastery); Mafia III 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.
Just Cause 2
Grapple-parachute flow rewards handling skill
Mafia III
Stealth takedowns and gunfights
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Just Cause 2
Enemy AI never adapts
Mafia III
Racket guards follow fixed AI
Just Cause 2 leans a little harder on variance, though the gap is small.
Just Cause 2
Sandbox chaos varies moment to moment
Mafia III
Open world is static
Mafia III leans a little harder on optimization, though the gap is small.
Just Cause 2
Chaos-point economy and settlement completion routing
Mafia III
District takeover loop and underboss assignments
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.