head to head
Neither is simply harder - they are hard in different places. Portal demands more execution; Victoria 3 demands more variance.

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

Optimization · Pure Optimization
Industrial-era economy sim; pops and markets above all.
Portal leans Optimization (Pure Optimization); Victoria 3 leans Optimization (Pure Optimization).
Portal leans clearly harder on execution.
Portal
Portal placement timing modest.
Victoria 3
no reflex
Victoria 3 leans clearly harder on reads.
Portal
No adversary modeling player.
Victoria 3
AI scripted, limited adaptation
Victoria 3 leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Victoria 3
events, market shocks
Victoria 3 leans a little harder on optimization, though the gap is small.
Portal
Pure puzzle-solving optimization.
Victoria 3
economy, pops, laws 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.