head to head
Neither is simply harder - they are hard in different places. Hades demands more optimization; Returnal demands more variance.

Optimization · Practiced Mastery
An action roguelike about building boon synergies while dodging scripted encounters.

Execution · Twitch Chaos
Bullet-hell roguelike third-person shooter.
Hades leans Optimization (Practiced Mastery); Returnal leans Execution (Twitch Chaos).
Returnal leans a little harder on execution, though the gap is small.
Hades
Dash-attack timing and dodging drive moment-to-moment fights.
Returnal
Bullet-hell dodge and aim under pressure
Returnal leans a little harder on reads, though the gap is small.
Hades
Enemies and bosses use scripted patterns, not adaptation.
Returnal
Bosses scripted, patterns not adaptive
Returnal leans clearly harder on variance.
Hades
Boon offers and room rewards randomise each run.
Returnal
Room layouts, parasites, items roguelike
Hades leans clearly harder on optimization.
Hades
Build synergies and weapon aspects are deep solvable theory.
Returnal
Build synergies and route 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.