head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is optimization, and it is a single point.

Optimization · Pure Optimization
A platformer puzzle game built around deducing and exploiting each world's unique time-manipulation rule.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.
Braid leans Optimization (Pure Optimization); Portal leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Braid
Precise jumps and time-rewind timing are load-bearing
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.
Braid
No opponent; solo platforming puzzle
Portal
No adversary modeling player.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Braid
All puzzles are deterministic and hand-crafted
Portal
Deterministic chambers; no randomness.
Braid leans a little harder on optimization, though the gap is small.
Braid
Understanding each world's time-manipulation rule and its exact solution is the game
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.