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

Optimization · Pure Optimization
Base-building strategy game about optimizing upgrade economy and raid compositions.

Optimization · Pure Optimization
Space 4X with politics and faction-specific economies.
Clash of Clans leans Optimization (Pure Optimization); Endless Space 2 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.
Clash of Clans
Troop drop placement is forgiving
Endless Space 2
turn-based
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Clash of Clans
Base layouts anticipate human attackers' habits
Endless Space 2
AI scripted, some MP
Endless Space 2 leans a little harder on variance, though the gap is small.
Clash of Clans
Matchmaking and unseen traps add uncertainty
Endless Space 2
system traits, anomalies
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Clash of Clans
Army comps, upgrade paths, and attack routing
Endless Space 2
economy, ships, populations 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.