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
Aiming at bloon waves while solving a tower-defense upgrade economy first-person.

Execution · Practiced Mastery
A cartoonish horde shooter sequel of planet-hopping monster massacres.
Apes vs Helium leans Execution (Practiced Mastery); Serious Sam 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.
Apes vs Helium
An aimbot popping every bloon would trivialise the waves
Serious Sam 2
Sustained horde-clearing aim and strafing
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Apes vs Helium
Bloons follow fixed tracks, nothing adapts
Serious Sam 2
Enemy waves are entirely scripted
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Apes vs Helium
Wave composition is learnable, little stays hidden
Serious Sam 2
Cartoon set-pieces surprise once
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Apes vs Helium
Upgrade and class economy against known waves is solvable
Serious Sam 2
Target priority and arena routes are learnable
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.