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
Reversal timing and pacing against an opponent baiting your counters.

Execution · Practiced Mastery
Reversal-timing execution with human habit-reading layered over wrestling systems.
WWE 2K15 leans Execution (Competitive PvP); WWE 2K23 leans Execution (Practiced Mastery).
WWE 2K23 leans a little harder on execution, though the gap is small.
WWE 2K15
Reversal timing windows decide most exchanges
WWE 2K23
Reversal timing windows and combo strings decide matches
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
WWE 2K15
Human opponents bait reversals and vary move timing
WWE 2K23
Human opponents reward baiting predictable reversal habits
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
WWE 2K15
Chain-wrestling rock-paper-scissors minigames add randomness
WWE 2K23
Match stipulations and AI logic add mild chaos
WWE 2K23 leans a little harder on optimization, though the gap is small.
WWE 2K15
Move sets, stamina and match pacing are learnable systems
WWE 2K23
Move-set knowledge, stamina and meta builds are studyable
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.