head to head
They Are Billions asks more than The Elder Scrolls V: Skyrim, and the gap is optimization.

Optimization · Pure Optimization
An open-world RPG mostly about discovering and stacking exploitable progression systems.

Optimization · Pure Optimization
Steampunk colony defense against scripted zombie waves.
The Elder Scrolls V: Skyrim leans Optimization (Pure Optimization); They Are Billions 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.
The Elder Scrolls V: Skyrim
Combat is forgiving; aim and timing rarely punish you.
They Are Billions
some pause-based defense placement
They Are Billions leans a little harder on reads, though the gap is small.
The Elder Scrolls V: Skyrim
Enemy AI is scripted and exploitable; not adaptive.
They Are Billions
zombie AI not adaptive
They Are Billions leans a little harder on variance, though the gap is small.
The Elder Scrolls V: Skyrim
Loot tables and leveled lists inject mild randomness.
They Are Billions
map gen, swarm timing
They Are Billions leans clearly harder on optimization.
The Elder Scrolls V: Skyrim
Skill stacking, enchant loops, and exploits are deeply solvable.
They Are Billions
economy and wall placement 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.