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

Optimization · Practiced Mastery
Threading precise inputs through scripted guard gauntlets aboard a controlled and memorisable facility.

Execution · Practiced Mastery
Plannable stealth routing punctuated by precise ballistic marksmanship.
Metal Gear Solid 2: Sons of Liberty leans Optimization (Practiced Mastery); Sniper Elite III leans Execution (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Metal Gear Solid 2: Sons of Liberty
First-person aim and guard reaction windows demand precise input
Sniper Elite III
Ballistic long shots demand steady, compensated aim
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Metal Gear Solid 2: Sons of Liberty
Guards radio for backup on scripted triggers, not adaptive tactics
Sniper Elite III
Enemy AI follows mappable alert and search routines
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Metal Gear Solid 2: Sons of Liberty
Alert timers and item pickups create some hidden-state tension
Sniper Elite III
Patrol details and wind vary slightly per attempt
Metal Gear Solid 2: Sons of Liberty leans a little harder on optimization, though the gap is small.
Metal Gear Solid 2: Sons of Liberty
Chokepoint memorisation and radar manipulation are learnable and repeatable
Sniper Elite III
Open maps reward planned routes, sound masking and relocation
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.