head to head
Warcraft III: Reign of Chaos asks more than Natural Selection 2, and the gap is optimization.

Execution · Grand Arena
Asymmetric FPS-RTS hybrid where aliens and marines fight under live human commanders.

Optimization · Grand Arena
Blizzard's hero-centric RTS where build-order theory meets surgical unit micro against humans.
Natural Selection 2 leans Execution (Grand Arena); Warcraft III: Reign of Chaos leans Optimization (Grand Arena).
Natural Selection 2 leans a little harder on execution, though the gap is small.
Natural Selection 2
Skulk movement and marine aim have steep ceilings
Warcraft III: Reign of Chaos
Micro of heroes and units decides fights
Warcraft III: Reign of Chaos leans a little harder on reads, though the gap is small.
Natural Selection 2
Human commanders mind-game tech and map control
Warcraft III: Reign of Chaos
Scouting and out-guessing a human opponent's tech
Warcraft III: Reign of Chaos leans a little harder on variance, though the gap is small.
Natural Selection 2
Symmetric maps, little randomness
Warcraft III: Reign of Chaos
Creep routes and item drops add randomness
Warcraft III: Reign of Chaos leans clearly harder on optimization.
Natural Selection 2
Tech trees, res flow, and lifeform timings
Warcraft III: Reign of Chaos
Build orders, creeping routes, and matchup theory run deep
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.