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

Optimization · Pure Optimization
A factory-engineering sandbox about scaling throughput against your own bottlenecks.

Optimization · Pure Optimization
The genre-defining cartoon tower defense with crunchy upgrades and fixed waves begging for perfect solutions.
Factorio leans Optimization (Pure Optimization); Kingdom Rush leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Factorio
Some APM in early hand-crafting; otherwise irrelevant.
Kingdom Rush
Light micro of hero and rally points
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Factorio
Biters follow fixed pollution rules; no adaptive opponent.
Kingdom Rush
Wave compositions are fixed and previewable
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Factorio
Resource patch placement adds minor map randomness.
Kingdom Rush
Almost fully deterministic waves
Factorio leans a little harder on optimization, though the gap is small.
Factorio
Throughput, ratios, and logistics are the entire game.
Kingdom Rush
Tower placement and upgrade routes are solvable
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.