head to head
Neither is simply harder - they are hard in different places. Portal demands more execution; Yakuza: Like a Dragon demands more variance.

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

Optimization · Pure Optimization
A turn-based Yakuza won by job-mastery and party-build routing.
Portal leans Optimization (Pure Optimization); Yakuza: Like a Dragon leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Portal
Portal placement timing modest.
Yakuza: Like a Dragon
Turn-based, minor positioning inputs
Yakuza: Like a Dragon leans a little harder on reads, though the gap is small.
Portal
No adversary modeling player.
Yakuza: Like a Dragon
Scripted enemies
Yakuza: Like a Dragon leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Yakuza: Like a Dragon
Job ability and drop rolls
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.
Yakuza: Like a Dragon
Job mastery and party-build routing central
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.