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
Combined-arms multiplayer shooter famous for map-altering levolution moments and 64-player conquest.

Execution · Competitive PvP
Tests shot timing and play-calling prediction against human defenders.
Battlefield 4 leans Execution (Competitive PvP); NBA 2K15 leans Execution (Competitive PvP).
Battlefield 4 leans a little harder on execution, though the gap is small.
Battlefield 4
Gunplay, vehicle mastery, and movement under fire
NBA 2K15
Shot-stick timing and dribble moves demand practiced hands
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Battlefield 4
Human teams adapt to flanks and levolution chokes
NBA 2K15
Versus humans, baiting defenders and calling counters drives possessions
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Battlefield 4
Map-altering events and spawns inject noise
NBA 2K15
Shot RNG and loose balls swing close games
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Battlefield 4
Loadout tuning and objective rotation knowledge
NBA 2K15
Playbooks, matchups and roster management reward system study
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.