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.

Variance · Light / Casual
Claustrophobic horror short about piloting a blind submarine through a blood ocean.

Optimization · Light / Casual
An underwater sci-fi horror about consciousness and identity.
Iron Lung leans Variance (Light / Casual); SOMA leans Optimization (Light / Casual).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Iron Lung
Slow submarine piloting by coordinates
SOMA
Light stealth, gentle inputs.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Iron Lung
The thing outside follows a script
SOMA
Creatures follow scripts.
Iron Lung leans a little harder on variance, though the gap is small.
Iron Lung
Blind navigation; you see only camera snapshots
SOMA
Some hiding spot variation.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Iron Lung
Plotting waypoints on the paper map
SOMA
Few systems to optimize.
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.