head to head
Neither is simply harder - they are hard in different places. Rivals of Aether demands more reads; StarCraft demands more optimization.

Reads · Grand Arena
A shield-less platform fighter where the absence of defensive options forces constant aggressive reads against human opponents.

Optimization · Grand Arena
A real-time strategy classic where perfected build orders and mechanical speed decide most matches.
Rivals of Aether leans Reads (Grand Arena); StarCraft leans Optimization (Grand Arena).
Rivals of Aether leans a little harder on execution, though the gap is small.
Rivals of Aether
Wavedash movement and off-stage edgeguards require real physical precision
StarCraft
APM and micro control ceiling is huge
Rivals of Aether leans clearly harder on reads.
Rivals of Aether
No shields forces constant adaptive prediction against human opponents
StarCraft
scouting and predicting human opponent builds
Rivals of Aether leans a little harder on variance, though the gap is small.
Rivals of Aether
Stage hazards add minor variance
StarCraft
minimal hidden info beyond fog of war
StarCraft leans clearly harder on optimization.
Rivals of Aether
Elemental mechanic interactions and matchup routing reward study
StarCraft
build orders and economy are near-solvable
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.