head to head
Neither is simply harder - they are hard in different places. Portal demands more execution; Rebel Cops demands more variance.

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

Optimization · Pure Optimization
A turn-based tactics game testing positioning and resource planning under hit-chance RNG.
Portal leans Optimization (Pure Optimization); Rebel Cops leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Portal
Portal placement timing modest.
Rebel Cops
Aiming is point-based, not twitch reflex
Rebel Cops leans a little harder on reads, though the gap is small.
Portal
No adversary modeling player.
Rebel Cops
Enemy AI is scripted, not adaptive modelling
Rebel Cops leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Rebel Cops
Hit chances and detection add real randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Portal
Pure puzzle-solving optimization.
Rebel Cops
Positioning, resource scarcity and turn planning decide missions
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.