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
A cartoonish horde shooter sequel of planet-hopping monster massacres.

Execution · Practiced Mastery
Ballistics compensation along tightly scripted sniping corridors.
Serious Sam 2 leans Execution (Practiced Mastery); Sniper: Ghost Warrior 2 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.
Serious Sam 2
Sustained horde-clearing aim and strafing
Sniper: Ghost Warrior 2
Breath control, wind and drop compensation on every shot
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Serious Sam 2
Enemy waves are entirely scripted
Sniper: Ghost Warrior 2
Enemies run scripted patrols and alarms
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Serious Sam 2
Cartoon set-pieces surprise once
Sniper: Ghost Warrior 2
Wind values randomise individual shot solutions
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Serious Sam 2
Target priority and arena routes are learnable
Sniper: Ghost Warrior 2
Memorising target sequences and stealth routes carries missions
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.