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 · Grand Arena
Open military simulator and PvP sandbox.

Execution · Competitive PvP
Gunplay and predicting human squads across large-scale and extraction modes.
Arma 3 leans Execution (Grand Arena); Delta Force leans Execution (Competitive PvP).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Arma 3
Bullet drop, stance, sway, weight all matter
Delta Force
Gunfights and recoil control decide most engagements
Arma 3 leans a little harder on reads, though the gap is small.
Arma 3
PvP and milsim ops reward prediction
Delta Force
Predicting human rotations and pushes runs through every mode
Arma 3 leans a little harder on variance, though the gap is small.
Arma 3
Mission scripts and AI behavior vary
Delta Force
Extraction loot and operator gadget chaos add noise
Arma 3 leans a little harder on optimization, though the gap is small.
Arma 3
Loadout planning and tactics solvable
Delta Force
Loadout economy and objective sequencing set the floor
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.