head to head
Neither is simply harder - they are hard in different places. Evotinction demands more variance; Portal demands more optimization.

Optimization · Pure Optimization
A tactical action game about a robot uprising against humanity's remnants.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Evotinction leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans a little harder on execution, though the gap is small.
Evotinction
squad control demands light tactical input
Portal
Portal placement timing modest.
Evotinction leans a little harder on reads, though the gap is small.
Evotinction
AI robots follow scripted combat behavior
Portal
No adversary modeling player.
Evotinction leans clearly harder on variance.
Evotinction
randomized encounters and mutation events
Portal
Deterministic chambers; no randomness.
Portal leans clearly harder on optimization.
Evotinction
squad and evolution system optimization
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.