head to head
Total War Saga: Thrones of Britannia asks more than Portal, and the gap is variance.

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

Optimization · Pure Optimization
A focused Total War set in Viking-age Britain, trading scale for tighter kingdom management.
Portal leans Optimization (Pure Optimization); Total War Saga: Thrones of Britannia leans Optimization (Pure Optimization).
Portal leans a little harder on execution, though the gap is small.
Portal
Portal placement timing modest.
Total War Saga: Thrones of Britannia
Real-time battle micro matters in close fights
Total War Saga: Thrones of Britannia leans clearly harder on reads.
Portal
No adversary modeling player.
Total War Saga: Thrones of Britannia
Multiplayer battles involve some human prediction
Total War Saga: Thrones of Britannia leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Total War Saga: Thrones of Britannia
Campaign events and AI moves add mild uncertainty
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Portal
Pure puzzle-solving optimization.
Total War Saga: Thrones of Britannia
Settlement planning and army composition decide the campaign
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.