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 · Practiced Mastery
Prequel chronicling Noble Team's doomed defence, with armour abilities reshaping multiplayer.

Execution · Competitive PvP
Shot timing and play selection against opponents adjusting to your tendencies.
Halo: Reach leans Execution (Practiced Mastery); NBA 2K14 leans Execution (Competitive PvP).
Halo: Reach leans a little harder on execution, though the gap is small.
Halo: Reach
DMR precision and armour-ability timing
NBA 2K14
Shot release timing and dribble chains gate scoring
NBA 2K14 leans a little harder on reads, though the gap is small.
Halo: Reach
Multiplayer rewards predicting human movement
NBA 2K14
Online opponents counter your favourite plays
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Halo: Reach
Loadouts and spawns add small swings
NBA 2K14
Shot RNG sways close possessions
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Halo: Reach
Ability matchups and map knowledge
NBA 2K14
Playbook knowledge and roster management reward 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.