head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is reads, and it is a single point.

Execution · Competitive PvP
Stick execution and reading human opponents within a meta-driven system.

Execution · Grand Arena
Console-friendly RTS where leader powers, base management, and Blitz card battles test both micro and opponent reading.
FIFA 18 leans Execution (Competitive PvP); Halo Wars 2 leans Execution (Grand Arena).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
FIFA 18
Perfect stick skill and timing dominate dribbles and finishing
Halo Wars 2
Leader power activation and Blitz card plays need precise timing
Halo Wars 2 leans a little harder on reads, though the gap is small.
FIFA 18
Human opponents bait, switch tactics and counter your habits
Halo Wars 2
Opponent leader choice and Blitz deck strategy must be predicted
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
FIFA 18
Bounce physics and pack luck add measured chaos
Halo Wars 2
Blitz card draw and resource crate spawns add moderate uncertainty
Halo Wars 2 leans a little harder on optimization, though the gap is small.
FIFA 18
Formation, squad chemistry and meta mechanics reward study
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.