head to head
Neither is simply harder - they are hard in different places. Portal demands more execution; Professor Layton vs. Phoenix Wright: Ace Attorney demands more variance.

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

Optimization · Pure Optimization
Authored logic puzzles and contradiction hunting with zero execution demand.
Portal leans Optimization (Pure Optimization); Professor Layton vs. Phoenix Wright: Ace Attorney leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Portal
Portal placement timing modest.
Professor Layton vs. Phoenix Wright: Ace Attorney
Tapping answers has no physical component
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Portal
No adversary modeling player.
Professor Layton vs. Phoenix Wright: Ace Attorney
Witnesses are scripted, contradictions are authored
Professor Layton vs. Phoenix Wright: Ace Attorney leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Professor Layton vs. Phoenix Wright: Ace Attorney
Testimony twists are hidden until revealed, then fixed
Portal leans a little harder on optimization, though the gap is small.
Portal
Pure puzzle-solving optimization.
Professor Layton vs. Phoenix Wright: Ace Attorney
Logic puzzles and contradiction-spotting are fully solvable
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.