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 · Competitive PvP
Large-scale modern combined-arms shooter built on destructible maps and squad teamwork.

Execution · Pure Mechanics
Multiplayer-focused Halo with the series' highest movement skill ceiling.
Battlefield 3 leans Execution (Competitive PvP); Halo 5: Guardians leans Execution (Pure Mechanics).
Halo 5: Guardians leans a little harder on execution, though the gap is small.
Battlefield 3
Gunplay, suppression management, and vehicle piloting
Halo 5: Guardians
Thrusters, clamber, and aim raise the ceiling
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Battlefield 3
Human teams adapt routes and armor pushes
Halo 5: Guardians
Arena ranked play is human-versus-human
Battlefield 3 leans a little harder on variance, though the gap is small.
Battlefield 3
Spawns, destruction, and vehicle drops shuffle engagements
Halo 5: Guardians
Spawns and REQ Warzone randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Battlefield 3
Unlock paths, class synergy, and map control
Halo 5: Guardians
Movement routes and weapon timers
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.