head to head
Returnal asks more than Helldivers 2, and the gap is execution.

Optimization · Practiced Mastery
Top-tier co-op shooter against bug and bot hordes.

Execution · Twitch Chaos
Bullet-hell roguelike third-person shooter.
Helldivers 2 leans Optimization (Practiced Mastery); Returnal leans Execution (Twitch Chaos).
Returnal leans clearly harder on execution.
Helldivers 2
Recoil, stratagem inputs, friendly-fire aim
Returnal
Bullet-hell dodge and aim under pressure
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Helldivers 2
Enemies scripted, no adaptive opponent
Returnal
Bosses scripted, patterns not adaptive
Returnal leans a little harder on variance, though the gap is small.
Helldivers 2
Patrol spawns and modifiers shake missions
Returnal
Room layouts, parasites, items roguelike
Helldivers 2 leans a little harder on optimization, though the gap is small.
Helldivers 2
Loadout and stratagem synergies deep
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.