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 · Competitive PvP
A rugby simulation testing input timing and tactical play against opponents.
Battlefield 3 leans Execution (Competitive PvP); Rugby World Cup 2015 leans Execution (Competitive PvP).
Battlefield 3 leans a little harder on execution, though the gap is small.
Battlefield 3
Gunplay, suppression management, and vehicle piloting
Rugby World Cup 2015
Timing passes, tackles, and kicks needs consistent inputs
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
Rugby World Cup 2015
Human opponents can be read in multiplayer matches
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Battlefield 3
Spawns, destruction, and vehicle drops shuffle engagements
Rugby World Cup 2015
Ball bounces and AI add some unpredictability
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
Rugby World Cup 2015
Set plays, team selection, and tactics form a systems layer
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.