head to head
Natural Selection 2 asks more than Insurgency, and the gap is optimization.

Execution · Competitive PvP
Hardcore team shooter where one bullet kills and the HUD tells you nothing.

Execution · Grand Arena
Asymmetric FPS-RTS hybrid where aliens and marines fight under live human commanders.
Insurgency leans Execution (Competitive PvP); Natural Selection 2 leans Execution (Grand Arena).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Insurgency
One-shot lethality rewards precise aim
Natural Selection 2
Skulk movement and marine aim have steep ceilings
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Insurgency
Human squads flank and adapt each round
Natural Selection 2
Human commanders mind-game tech and map control
Insurgency leans a little harder on variance, though the gap is small.
Insurgency
No killcam or HUD hides enemy positions
Natural Selection 2
Symmetric maps, little randomness
Natural Selection 2 leans clearly harder on optimization.
Insurgency
Loadout points and objective route knowledge
Natural Selection 2
Tech trees, res flow, and lifeform timings
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.