head to head
Left 4 Dead 2 asks more than S.T.A.L.K.E.R.: Shadow of Chernobyl, and the gap is reads.

Execution · Practiced Mastery
Co-op zombie shooter with adaptive AI Director.

Optimization · Practiced Mastery
An atmospheric open-zone survival shooter set in the Chernobyl exclusion zone.
Left 4 Dead 2 leans Execution (Practiced Mastery); S.T.A.L.K.E.R.: Shadow of Chernobyl leans Optimization (Practiced Mastery).
Left 4 Dead 2 leans a little harder on execution, though the gap is small.
Left 4 Dead 2
Headshots under horde pressure need aim
S.T.A.L.K.E.R.: Shadow of Chernobyl
Ballistic gunplay punishes sloppy aim
Left 4 Dead 2 leans clearly harder on reads.
Left 4 Dead 2
Versus special-infected ambushes have reads
S.T.A.L.K.E.R.: Shadow of Chernobyl
A-Life feels alive but doesn't model you
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Left 4 Dead 2
AI Director randomizes spawns and items
S.T.A.L.K.E.R.: Shadow of Chernobyl
Anomalies, mutant spawns, and artifact RNG hide information
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Left 4 Dead 2
Route knowledge and weapon picks solvable
S.T.A.L.K.E.R.: Shadow of Chernobyl
Artifact economy, routes, and stash knowledge converge
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.