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 · Systems & Chaos
Seminal 1994 strategy game mixing global base management with brutal turn-based alien squad combat.

Optimization · Pure Optimization
Faithful X-COM successor managing a global war against alien invasion.
X-COM: UFO Defense leans Optimization (Systems & Chaos); Xenonauts leans Optimization (Pure Optimization).
X-COM: UFO Defense leans a little harder on execution, though the gap is small.
X-COM: UFO Defense
Turn-based; only inventory clicking
Xenonauts
Turn-based; no physical demands.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
X-COM: UFO Defense
Alien AI is scripted, never adaptive
Xenonauts
Alien AI follows consistent behavior rules.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
X-COM: UFO Defense
Hit rolls, random maps, and unseen aliens punish constantly
Xenonauts
Hit rolls and unseen alien positions punish certainty.
Xenonauts leans a little harder on optimization, though the gap is small.
X-COM: UFO Defense
Base economy, research order, and tactical doctrine are masterable
Xenonauts
Air war, economy and squad doctrine decide campaigns.
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.