head to head
Neither is simply harder - they are hard in different places. Emperor: Rise of the Middle Kingdom demands more variance; Portal demands more execution.

Optimization · Pure Optimization
Ancient China city builder about elegant housing-block logistics.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Emperor: Rise of the Middle Kingdom leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Emperor: Rise of the Middle Kingdom
Pausable city placement, no pressure
Portal
Portal placement timing modest.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Emperor: Rise of the Middle Kingdom
No adaptive opposition
Portal
No adversary modeling player.
Emperor: Rise of the Middle Kingdom leans clearly harder on variance.
Emperor: Rise of the Middle Kingdom
Invasions and events on known schedules
Portal
Deterministic chambers; no randomness.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Emperor: Rise of the Middle Kingdom
Walker logistics and feng shui block planning
Portal
Pure puzzle-solving 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.