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 · Practiced Mastery
An arena fighter mixing combo execution, build grinding and human prediction online.

Execution · Competitive PvP
Tests shot timing and play-calling prediction against human defenders.
Dragon Ball: Xenoverse leans Execution (Practiced Mastery); NBA 2K15 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.
Dragon Ball: Xenoverse
3D arena combos, vanishes and ki management need practiced hands
NBA 2K15
Shot-stick timing and dribble moves demand practiced hands
NBA 2K15 leans a little harder on reads, though the gap is small.
Dragon Ball: Xenoverse
Online PvP rewards predicting human mixups; PvE is scripted
NBA 2K15
Versus humans, baiting defenders and calling counters drives possessions
NBA 2K15 leans a little harder on variance, though the gap is small.
Dragon Ball: Xenoverse
Skill drops from missions roll randomly
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.
Dragon Ball: Xenoverse
Build crafting and attribute allocation shape PvP viability
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.