head to head
Thief Gold asks more than Portal, and the gap is variance.

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

Optimization · Pure Optimization
Planning quiet routes through guarded spaces using light and sound as solvable systems.
Portal leans Optimization (Pure Optimization); Thief Gold 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.
Portal
Portal placement timing modest.
Thief Gold
Careful movement and timing past guards, but slow-paced
Thief Gold leans a little harder on reads, though the gap is small.
Portal
No adversary modeling player.
Thief Gold
Guard AI reacts to noise via fixed rules, never models you
Thief Gold leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Thief Gold
Unscripted patrols and unknown layouts hide information first time through
Portal leans a little harder on optimization, though the gap is small.
Portal
Pure puzzle-solving optimization.
Thief Gold
Route planning, light management and loot sweeps converge to mastery
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.