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.

Optimization · Grand Arena
A real-time strategy classic where perfected build orders and mechanical speed decide most matches.

Optimization · Grand Arena
Large-scale RTS testing economic optimization, multitask speed and prediction of human build choices.
StarCraft leans Optimization (Grand Arena); Supreme Commander 2 leans Optimization (Grand Arena).
StarCraft leans a little harder on execution, though the gap is small.
StarCraft
APM and micro control ceiling is huge
Supreme Commander 2
Macro APM across huge armies separates skirmish winners
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
StarCraft
scouting and predicting human opponent builds
Supreme Commander 2
Multiplayer rewards scouting and predicting a human's tech switches
Supreme Commander 2 leans a little harder on variance, though the gap is small.
StarCraft
minimal hidden info beyond fog of war
Supreme Commander 2
Open maps leave little hidden beyond fog of war
StarCraft leans a little harder on optimization, though the gap is small.
StarCraft
build orders and economy are near-solvable
Supreme Commander 2
Economy ratios, build orders and research routing are deeply 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.