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

Optimization · Pure Optimization
An open-ended needs-and-money system that rewards efficient scheduling.

Optimization · Pure Optimization
A story-driven survival adventure alone on a hostile alien planet.
The Sims leans Optimization (Pure Optimization); The Solus Project leans Optimization (Pure Optimization).
The Solus Project leans a little harder on execution, though the gap is small.
The Sims
Clicking menus has no physical ceiling
The Solus Project
Exploration platforming with mild precision needs
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
The Sims
Sims run need-driven scripts, not minds
The Solus Project
No adaptive entities, only environment
The Solus Project leans a little harder on variance, though the gap is small.
The Sims
Event rolls add flavour, all quickly mapped
The Solus Project
Alien caves hidden until explored, single playthrough mostly
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
The Sims
Need scheduling, career grinding and money loops are solvable
The Solus Project
Managing temperature, hunger, and route planning drives survival
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.