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
Arcade monster wrestling testing grapple timing and versus-mode throw mindgames.

Execution · Competitive PvP
Reversal timing and pacing against an opponent baiting your counters.
King of the Monsters leans Execution (Competitive PvP); WWE 2K15 leans Execution (Competitive PvP).
King of the Monsters leans a little harder on execution, though the gap is small.
King of the Monsters
Grapple timing and positioning decide monster bouts
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.
King of the Monsters
Versus humans, throw-tech mindgames add real prediction
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.
King of the Monsters
Grapple outcomes carry arcade-era randomness
WWE 2K15
Chain-wrestling rock-paper-scissors minigames add randomness
WWE 2K15 leans a little harder on optimization, though the gap is small.
King of the Monsters
Small movesets converge to known optimal loops fast
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.