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

Optimization · Pure Optimization
A first-person farming game about wrangling adorable slimes for plorts.

Optimization · Pure Optimization
A story-driven survival adventure alone on a hostile alien planet.
Slime Rancher leans Optimization (Pure Optimization); The Solus Project 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.
Slime Rancher
Vacuum aiming is gentle.
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.
Slime Rancher
Slimes follow scripted behaviors.
The Solus Project
No adaptive entities, only environment
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Slime Rancher
Plort prices and slime spawns vary.
The Solus Project
Alien caves hidden until explored, single playthrough mostly
Slime Rancher leans a little harder on optimization, though the gap is small.
Slime Rancher
Ranch layout and economy reward planning.
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.