head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Optimization · Pure Optimization
A tropical farming life-sim about reviving an island community.

Optimization · Pure Optimization
A first-person farming game about wrangling adorable slimes for plorts.
Coral Island leans Optimization (Pure Optimization); Slime Rancher 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.
Coral Island
Farming inputs are gentle.
Slime Rancher
Vacuum aiming is gentle.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Coral Island
Villagers follow scripted schedules.
Slime Rancher
Slimes follow scripted behaviors.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Coral Island
Crop quality and fishing have RNG.
Slime Rancher
Plort prices and slime spawns vary.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Coral Island
Farm planning and bundle routing reward optimization.
Slime Rancher
Ranch layout and economy reward planning.
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.