head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is variance, and it is a single point.

Execution · Competitive PvP
Shot timing and play-calling against opponents who scheme around your habits.

Execution · Competitive PvP
Tests shot-stick timing and badge-build optimization against human defenders.
NBA 2K16 leans Execution (Competitive PvP); NBA 2K20 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.
NBA 2K16
Shot-stick timing and dribble moves gate every possession
NBA 2K20
Shot timing and dribble combos require practiced stick work
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
NBA 2K16
Online opponents adjust defensive schemes against your tendencies
NBA 2K20
Outguessing human defenders and callers decides online possessions
NBA 2K20 leans a little harder on variance, though the gap is small.
NBA 2K16
Shot RNG and card packs add bounded randomness
NBA 2K20
Shot RNG and rebounds swing tight games
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
NBA 2K16
Playbooks, rotations and roster building reward deep study
NBA 2K20
Builds, badges and playbook knowledge dominate MyCareer and online
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.