head to head
Neither is simply harder - they are hard in different places. Portal demands more execution; Sid Meier's Colonization demands more variance.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.

Optimization · Pure Optimization
A 1994 Sid Meier strategy game about building colonial economies and winning independence.
Portal leans Optimization (Pure Optimization); Sid Meier's Colonization leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Portal
Portal placement timing modest.
Sid Meier's Colonization
Turn-based; hands irrelevant
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Portal
No adversary modeling player.
Sid Meier's Colonization
Royal and rival AI behave on fixed schedules
Sid Meier's Colonization leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Sid Meier's Colonization
Random New World maps and native placement vary starts
Sid Meier's Colonization leans a little harder on optimization, though the gap is small.
Portal
Pure puzzle-solving optimization.
Sid Meier's Colonization
Production chains and liberty-bell timing are a solvable economy
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.