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 turn-based 4X where empire optimization beats turn-by-turn tactics.

Optimization · Pure Optimization
An open-source hex strategy game famous for its luck-laced combat rolls.
Civilization VI leans Optimization (Pure Optimization); The Battle for Wesnoth 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.
Civilization VI
Turn-based, no mechanical input demands.
The Battle for Wesnoth
Turn-based hex moves, no dexterity.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Civilization VI
AI is scripted; multiplayer adds light adaptation.
The Battle for Wesnoth
Multiplayer opponents adapt; campaigns scripted.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Civilization VI
Map gen, barbarians, and city-state quests vary.
The Battle for Wesnoth
To-hit rolls swing battles constantly.
Civilization VI leans a little harder on optimization, though the gap is small.
Civilization VI
Tech, civics, and yield routing dominate strategy.
The Battle for Wesnoth
Unit matchups, terrain, and economy 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.