head to head
StarCraft II: Wings of Liberty asks more than Warcraft III: Reign of Chaos, and the gap is execution.

Execution · Grand Arena
Real-time strategy where hands, reads, and build optimization all matter at the top.

Optimization · Grand Arena
Blizzard's hero-centric RTS where build-order theory meets surgical unit micro against humans.
StarCraft II: Wings of Liberty leans Execution (Grand Arena); Warcraft III: Reign of Chaos leans Optimization (Grand Arena).
StarCraft II: Wings of Liberty leans clearly harder on execution.
StarCraft II: Wings of Liberty
APM, macro, micro-control under pressure
Warcraft III: Reign of Chaos
Micro of heroes and units decides fights
StarCraft II: Wings of Liberty leans a little harder on reads, though the gap is small.
StarCraft II: Wings of Liberty
1v1 ladder vs adaptive humans modeling you
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.
StarCraft II: Wings of Liberty
map spawns minor; mostly known
Warcraft III: Reign of Chaos
Creep routes and item drops add randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
StarCraft II: Wings of Liberty
build orders, economy curves heavily solved
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.