head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Optimization · Pure Optimization
Side-on turn-based tactics where you manually aim ricocheting bullets for a steambot pirate crew.

Optimization · Pure Optimization
A tactical squad shooter where positioning and probability management outweigh raw aim.
SteamWorld Heist leans Optimization (Pure Optimization); The Bureau: XCOM Declassified 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.
SteamWorld Heist
Manual aim and ricochet shots reward steady hands
The Bureau: XCOM Declassified
cover shooting timing is moderate
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
SteamWorld Heist
Enemy bots follow fixed behaviors
The Bureau: XCOM Declassified
alien AI is scripted, no adaptation
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
SteamWorld Heist
Procedural ship layouts and loot drops
The Bureau: XCOM Declassified
cover-based hit chances are randomized
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
SteamWorld Heist
Crew builds, weapon picks, and turn routing carry runs
The Bureau: XCOM Declassified
squad tactics and builds 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.