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 near-future Call of Duty with squad-focused multiplayer and the Extinction mode.

Execution · Pure Mechanics
Heavy first-person gunplay testing aim, with positional prediction in multiplayer.
Call of Duty: Ghosts leans Execution (Practiced Mastery); Killzone 3 leans Execution (Pure Mechanics).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty: Ghosts
Fast time-to-kill rewards first-shot aim
Killzone 3
Weighty gunplay still demands aim and recoil control
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty: Ghosts
Outguessing human routes and peeks matters
Killzone 3
Multiplayer opponents flank and bait; campaign AI is scripted
Call of Duty: Ghosts leans a little harder on variance, though the gap is small.
Call of Duty: Ghosts
Spawns and lobby matchups add noise
Killzone 3
Spawns and spread inject limited randomness
Call of Duty: Ghosts leans a little harder on optimization, though the gap is small.
Call of Duty: Ghosts
Loadout and map knowledge are solvable layers
Killzone 3
Map control, loadouts and class roles structure multiplayer
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.