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

Execution · Practiced Mastery
Arena fighting where builds and combo execution meet light PvP prediction.

Execution · Competitive PvP
Reversal timing and pacing against an opponent baiting your counters.
Dragon Ball: Xenoverse 2 leans Execution (Practiced Mastery); WWE 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 2
Combo strings and vanish timing need moderate hands
WWE 2K15
Reversal timing windows decide most exchanges
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Dragon Ball: Xenoverse 2
PvP opponents bait supers and punish habits
WWE 2K15
Human opponents bait reversals and vary move timing
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Dragon Ball: Xenoverse 2
QQ Bang crafting and drop rates randomise builds
WWE 2K15
Chain-wrestling rock-paper-scissors minigames add randomness
Dragon Ball: Xenoverse 2 leans a little harder on optimization, though the gap is small.
Dragon Ball: Xenoverse 2
Build stats and skill loadouts shape every matchup
WWE 2K15
Move sets, stamina and match pacing are learnable systems
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.