head to head
Total War: Rome II asks more than Portal, and the gap is variance.

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

Optimization · Pure Optimization
Maintaining senate favor and province chains while executing real-time cohort tactics.
Portal leans Optimization (Pure Optimization); Total War: Rome II leans Optimization (Pure Optimization).
Total War: Rome II leans a little harder on execution, though the gap is small.
Portal
Portal placement timing modest.
Total War: Rome II
Cohort line management and flanking cavalry demand real-time micro
Total War: Rome II leans clearly harder on reads.
Portal
No adversary modeling player.
Total War: Rome II
AI generals follow scripted behaviors without adapting to the player
Total War: Rome II leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Total War: Rome II
Random political events and dynastic loyalty shifts add campaign variance
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: Rome II
Senate favor management and province chains form a solvable campaign system
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.