head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is execution, and it is a single point.

Optimization · Pure Optimization
Crafting-tree planning and needs management under light zombie pressure.

Optimization · Pure Optimization
A 2D sandbox of procedurally generated planets driven by crafting progression.
How to Survive leans Optimization (Pure Optimization); Starbound leans Optimization (Pure Optimization).
How to Survive leans a little harder on execution, though the gap is small.
How to Survive
Twin-stick zombie kiting needs modest aim
Starbound
Light platforming and combat, generous margins
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
How to Survive
Zombies are mindless scripted pressure
Starbound
Procedural NPCs follow simple fixed behaviours
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
How to Survive
Scavenged materials and island layouts are unknown until explored
Starbound
Procedural planets and loot keep early exploration unknown
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
How to Survive
Crafting trees and needs management decide survival
Starbound
Gear tiers, farming, and progression routes dominate
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.