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

Execution · Practiced Mastery
Weighty corridor shooting through scripted encounters with light loadout choice.

Execution · Practiced Mastery
Tests arcade grapple timing with shallow systems underneath.
Killzone leans Execution (Practiced Mastery); WCW Nitro leans Execution (Practiced Mastery).
Killzone leans a little harder on execution, though the gap is small.
Killzone
Heavy gunplay still rewards aim and positioning
WCW Nitro
Fast grapple timing in an arcade-paced wrestling frame
WCW Nitro leans a little harder on reads, though the gap is small.
Killzone
Campaign Helghast follow scripts; servers are long dead
WCW Nitro
Human versus play rewards mild move prediction
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Killzone
Encounters are fixed and replayable
WCW Nitro
Little randomness beyond AI behaviour
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Killzone
Character choice and route knowledge solve each level
WCW Nitro
Learning each wrestler's move list is quickly exhausted
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.