head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is variance, and it is a single point.

Optimization · Pure Optimization
A landmark strategy game combining a turn-based campaign for control of Rome with massive real-time battles.

Optimization · Pure Optimization
A focused Total War set in Viking-age Britain, trading scale for tighter kingdom management.
Rome: Total War leans Optimization (Pure Optimization); Total War Saga: Thrones of Britannia 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.
Rome: Total War
Real-time battle micro rewards quick unit handling
Total War Saga: Thrones of Britannia
Real-time battle micro matters in close fights
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Rome: Total War
Optional multiplayer battles; campaign AI is mappable
Total War Saga: Thrones of Britannia
Multiplayer battles involve some human prediction
Total War Saga: Thrones of Britannia leans a little harder on variance, though the gap is small.
Rome: Total War
Diplomacy and AI moves add modest fog
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.
Rome: Total War
Campaign economy, recruitment, and battle tactics are solvable
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.