head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is reads, and it is a single point.

Optimization · Mind & Math
Economy and formation optimisation at huge scale against adapting human strategy.

Optimization · Pure Optimization
Large-scale RTS famous for strategic zoom, thousand-unit armies, and a streaming mass-energy economy.
Cossacks: European Wars leans Optimization (Mind & Math); Supreme Commander leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Cossacks: European Wars
Managing thousands of units strains APM and attention
Supreme Commander
Massive APM demands across strategic-zoom battlefields
Cossacks: European Wars leans a little harder on reads, though the gap is small.
Cossacks: European Wars
Human opponents shift compositions and timing attacks
Supreme Commander
PvP hinges on scouting and countering opponent commitments
Cossacks: European Wars leans a little harder on variance, though the gap is small.
Cossacks: European Wars
Map resources and scouting gaps hide information early
Supreme Commander
Deterministic engine; only unscouted intel
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Cossacks: European Wars
Economy ratios, tech order and formation math dominate outcomes
Supreme Commander
Streaming economy and build-order efficiency are the backbone
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.