head to head
Risk of Rain asks more than Rain World, and the gap is optimization.

Variance · Twitch Chaos
A brutal survival platformer where you are prey in a living, indifferent ecosystem.

Optimization · Practiced Mastery
Side-scrolling roguelike where item synergies snowball against a relentless difficulty clock.
Rain World leans Variance (Twitch Chaos); Risk of Rain leans Optimization (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Rain World
Momentum-based movement and spear throws are slippery and demanding
Risk of Rain
Dodging projectiles and platforming under scaling pressure.
Rain World leans a little harder on reads, though the gap is small.
Rain World
Predator AI is dynamic simulation, not modeling of you
Risk of Rain
Enemies spawn and chase; no adaptation.
Rain World leans a little harder on variance, though the gap is small.
Rain World
Creature placement and behavior shift unpredictably each cycle
Risk of Rain
Item drops and stage rolls dominate run identity.
Risk of Rain leans clearly harder on optimization.
Rain World
Route knowledge and ecosystem mastery slowly tame the chaos
Risk of Rain
Item stacking and time-pressure routing is solvable.
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.