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
Strategy sim about evolving a pathogen to outpace the world's cure effort.

Optimization · Pure Optimization
The 2001 Civilization entry that introduced culture, strategic resources and refined empire micromanagement.
Plague Inc. leans Optimization (Pure Optimization); Sid Meier's Civilization III 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.
Plague Inc.
Tapping menus only
Sid Meier's Civilization III
No dexterity in a turn-based interface
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Plague Inc.
World response is algorithmic, not adaptive to you
Sid Meier's Civilization III
AI personalities are fixed and mappable
Sid Meier's Civilization III leans a little harder on variance, though the gap is small.
Plague Inc.
Spread events and cure pace fluctuate
Sid Meier's Civilization III
Random maps, resources and combat rolls matter early
Sid Meier's Civilization III leans a little harder on optimization, though the gap is small.
Plague Inc.
Evolution-point timing strategies are largely solved
Sid Meier's Civilization III
Corruption math, worker turns and culture borders reward deep optimization
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.