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 · Pure Optimization
Optimizing city placement, social policies, and victory routing under randomized map unknowns.

Optimization · Pure Optimization
Designing ships and spreading influence across a randomly generated galaxy through deep optimization.
Civilization V leans Optimization (Pure Optimization); Galactic Civilizations III leans Optimization (Pure Optimization).
Civilization V leans a little harder on execution, though the gap is small.
Civilization V
UI actions need no precision; speed is not a factor
Galactic Civilizations III
Fully turn-based; no physical skill axis
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Civilization V
AI follows scripted personalities, not genuine player modelling
Galactic Civilizations III
AI races have static personalities and no adaptive opponent modelling
Civilization V leans a little harder on variance, though the gap is small.
Civilization V
Random starts, barbarian spawns, and goody huts create hidden unknowns
Galactic Civilizations III
Random galaxy layouts and events add manageable unknowns
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Civilization V
Hex placement, social policies, and victory routing are fully solvable
Galactic Civilizations III
Ship design, influence spreading, and tech tree form a deep optimization puzzle
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.