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 · Practiced Mastery
A strategy shooter testing defense placement economy backed by active gunplay.

Optimization · Pure Optimization
A tactical squad shooter where positioning and probability management outweigh raw aim.
Fortified leans Optimization (Practiced Mastery); The Bureau: XCOM Declassified leans Optimization (Pure Optimization).
Fortified leans a little harder on execution, though the gap is small.
Fortified
Third-person shooting between waves keeps hands busy
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.
Fortified
Martian waves are scripted compositions
The Bureau: XCOM Declassified
alien AI is scripted, no adaptation
The Bureau: XCOM Declassified leans a little harder on variance, though the gap is small.
Fortified
Wave makeup is known after a single attempt
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.
Fortified
Defense placement and hero loadout economy decide rounds
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.