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

Execution · Competitive PvP
Punishing asymmetric Vietnam shooter where positioning beats twitch reflexes.
Insurgency leans Execution (Competitive PvP); Rising Storm 2: Vietnam leans Execution (Competitive PvP).
Insurgency leans a little harder on execution, though the gap is small.
Insurgency
One-shot lethality rewards precise aim
Rising Storm 2: Vietnam
One-shot lethality makes aim and exposure discipline decisive.
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
Rising Storm 2: Vietnam
Predicting human pushes, flanks, and tunnel placements.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Insurgency
No killcam or HUD hides enemy positions
Rising Storm 2: Vietnam
Smoke, foliage concealment, and unseen enemies.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Insurgency
Loadout points and objective route knowledge
Rising Storm 2: Vietnam
Map lanes, commander assets, and role kits 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.