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

Optimization · Pure Optimization
Dystopian management adventure about a landlord spying on tenants for a totalitarian state.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Beholder leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Beholder
Simple point-and-click landlord actions
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.
Beholder
Tenants follow scripted schedules, not adaptive
Portal
No adversary modeling player.
Beholder leans clearly harder on variance.
Beholder
Tenant events and directives surprise first runs
Portal
Deterministic chambers; no randomness.
Portal leans a little harder on optimization, though the gap is small.
Beholder
Money, time, and blackmail decision routing
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.