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

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

Optimization · Pure Optimization
Hidden-object hunting and fixed machine puzzles testing observation and deduction.
Portal leans Optimization (Pure Optimization); The Tiny Bang Story leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Portal
Portal placement timing modest.
The Tiny Bang Story
Clicking hidden objects has no physical ceiling
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 Tiny Bang Story
No opponent exists in a wordless puzzle world
The Tiny Bang Story leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
The Tiny Bang Story
Hidden items stay unknown only until spotted
Portal leans clearly harder on optimization.
Portal
Pure puzzle-solving optimization.
The Tiny Bang Story
Each machine puzzle has one fixed deducible solution
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.