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

Execution · Practiced Mastery
Plannable stealth routing punctuated by precise ballistic marksmanship.

Execution · Practiced Mastery
The sequel-remake pairing Butcher Bay with a new stealth-action campaign aboard a mercenary ship.
Sniper Elite III leans Execution (Practiced Mastery); The Chronicles of Riddick: Assault on Dark Athena 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.
Sniper Elite III
Ballistic long shots demand steady, compensated aim
The Chronicles of Riddick: Assault on Dark Athena
Melee takedowns and gunplay demand reliable hands
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Sniper Elite III
Enemy AI follows mappable alert and search routines
The Chronicles of Riddick: Assault on Dark Athena
Drone and guard behavior is fully scripted
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Sniper Elite III
Patrol details and wind vary slightly per attempt
The Chronicles of Riddick: Assault on Dark Athena
First-run uncertainty about patrols and drone placements
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Sniper Elite III
Open maps reward planned routes, sound masking and relocation
The Chronicles of Riddick: Assault on Dark Athena
Stealth routes and encounter solutions are learnable fixed content
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.