head to head
Neither is simply harder - they are hard in different places. Portal demands more execution; Rise of Kingdoms demands more reads.

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

Optimization · Pure Optimization
Long-horizon resource and commander optimization with alliance-war prediction at the top end.
Portal leans Optimization (Pure Optimization); Rise of Kingdoms leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Portal
Portal placement timing modest.
Rise of Kingdoms
Tapping commands has no physical ceiling
Rise of Kingdoms leans clearly harder on reads.
Portal
No adversary modeling player.
Rise of Kingdoms
Alliance wars involve outguessing rival players' timing and targets
Rise of Kingdoms leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Rise of Kingdoms
Commander pulls and event rolls gate progression
Portal leans a little harder on optimization, though the gap is small.
Portal
Pure puzzle-solving optimization.
Rise of Kingdoms
Build queues, commander pairings and resource math dominate
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.