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 · Pure Optimization
WWII grand strategy: templates, production, and focus paths.

Optimization · Pure Optimization
A turn-based tactics game about maneuvering units to outmatch the enemy.
Hearts of Iron IV leans Optimization (Pure Optimization); Tiny Metal: Full Metal Rumble leans Optimization (Pure Optimization).
Hearts of Iron IV leans a little harder on execution, though the gap is small.
Hearts of Iron IV
pausable, micromanagement-heavy
Tiny Metal: Full Metal Rumble
Issuing unit orders has no twitch demand
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Hearts of Iron IV
PvP partly, mostly scripted AI
Tiny Metal: Full Metal Rumble
Human opponents reward predicting their advances
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Hearts of Iron IV
focus tree branches, events
Tiny Metal: Full Metal Rumble
Some combat rolls and fog add uncertainty
Hearts of Iron IV leans a little harder on optimization, though the gap is small.
Hearts of Iron IV
division templates and production solved
Tiny Metal: Full Metal Rumble
Unit composition, terrain and economy decide battles
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.