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

Execution · Competitive PvP
Fast mech duels testing piloting execution and prediction of human opponents.
Battlefield 3 leans Execution (Competitive PvP); Mecha Break 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.
Battlefield 3
Gunplay, suppression management, and vehicle piloting
Mecha Break
Boost management and aim in fast mech duels demand dexterity
Mecha Break leans a little harder on reads, though the gap is small.
Battlefield 3
Human teams adapt routes and armor pushes
Mecha Break
Human pilots adapt positioning and engage timing constantly
Battlefield 3 leans a little harder on variance, though the gap is small.
Battlefield 3
Spawns, destruction, and vehicle drops shuffle engagements
Mecha Break
Match conditions are mostly fixed beyond extraction-mode loot
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
Mecha Break
Mech loadouts and role matchups reward roster knowledge
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.