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.

Execution · Grand Arena
Open military simulator and PvP sandbox.

Execution · Grand Arena
Console-friendly RTS where leader powers, base management, and Blitz card battles test both micro and opponent reading.
Arma 3 leans Execution (Grand Arena); Halo Wars 2 leans Execution (Grand Arena).
Arma 3 leans a little harder on execution, though the gap is small.
Arma 3
Bullet drop, stance, sway, weight all matter
Halo Wars 2
Leader power activation and Blitz card plays need precise timing
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Arma 3
PvP and milsim ops reward prediction
Halo Wars 2
Opponent leader choice and Blitz deck strategy must be predicted
Arma 3 leans a little harder on variance, though the gap is small.
Arma 3
Mission scripts and AI behavior vary
Halo Wars 2
Blitz card draw and resource crate spawns add moderate uncertainty
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Arma 3
Loadout planning and tactics solvable
Halo Wars 2
Leader power cooldown sequencing and base slot assignment are learnable
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.