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
Growing a floating base by solving resource chains and research order against scripted ocean threats.

Optimization · Pure Optimization
A story-driven survival adventure alone on a hostile alien planet.
Raft 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.
Raft
Shark hook-attacks require minimal timing
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.
Raft
Shark and seagull AI are scripted with no player modelling
The Solus Project
No adaptive entities, only environment
Raft leans a little harder on variance, though the gap is small.
Raft
Island loot tables and resource drift introduce randomness
The Solus Project
Alien caves hidden until explored, single playthrough mostly
Raft leans a little harder on optimization, though the gap is small.
Raft
Raft expansion, food chains, and research order are solvable systems
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.