head to head
Neither is simply harder - they are hard in different places. Hearthstone demands more variance; StarCraft demands more execution.

Variance · Grand Arena
A digital card game balancing opponent reads against draw variance.

Optimization · Grand Arena
A real-time strategy classic where perfected build orders and mechanical speed decide most matches.
Hearthstone leans Variance (Grand Arena); StarCraft leans Optimization (Grand Arena).
StarCraft leans clearly harder on execution.
Hearthstone
Clicks only, no mechanical skill
StarCraft
APM and micro control ceiling is huge
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Hearthstone
Human opponents bluff and adapt mid-match
StarCraft
scouting and predicting human opponent builds
Hearthstone leans clearly harder on variance.
Hearthstone
Draw RNG and discover effects swing games
StarCraft
minimal hidden info beyond fog of war
StarCraft leans clearly harder on optimization.
Hearthstone
Deckbuilding, mulligans, and mana curves matter
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.