head to head
Portal asks more than The Missing: J.J. Macfield and the Island of Memories, and the gap is optimization.

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

Optimization · Pure Optimization
Body-altering puzzle platforming where each obstacle has an intended grim solution.
Portal leans Optimization (Pure Optimization); The Missing: J.J. Macfield and the Island of Memories leans Optimization (Pure Optimization).
Portal leans a little harder on execution, though the gap is small.
Portal
Portal placement timing modest.
The Missing: J.J. Macfield and the Island of Memories
Platforming is deliberately loose and forgiving
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.
The Missing: J.J. Macfield and the Island of Memories
No adaptive opposition exists
The Missing: J.J. Macfield and the Island of Memories leans a little harder on variance, though the gap is small.
Portal
Deterministic chambers; no randomness.
The Missing: J.J. Macfield and the Island of Memories
Hand-crafted puzzles, fixed every run
Portal leans clearly harder on optimization.
Portal
Pure puzzle-solving optimization.
The Missing: J.J. Macfield and the Island of Memories
Using self-mutilation mechanics correctly per puzzle is the test
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.