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
A cozy island life-sim about building a community at your pace.

Optimization · Pure Optimization
A story-driven survival adventure alone on a hostile alien planet.
Animal Crossing: New Horizons 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.
Animal Crossing: New Horizons
Trivial inputs.
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.
Animal Crossing: New Horizons
NPCs are scripted.
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.
Animal Crossing: New Horizons
Daily visitors and fossils randomize.
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.
Animal Crossing: New Horizons
Turnips, layout, and time-routing 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.