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
A wrestling game testing reversal timing with light mind-games against humans.

Execution · Competitive PvP
Reversal timing and pacing against an opponent baiting your counters.
TNA Impact! leans Execution (Competitive PvP); WWE 2K15 leans Execution (Competitive PvP).
TNA Impact! leans a little harder on execution, though the gap is small.
TNA Impact!
Reversal timing windows decide most exchanges
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.
TNA Impact!
Human opponents can be baited into whiffed grapples
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.
TNA Impact!
Little is hidden beyond minor AI inconsistency
WWE 2K15
Chain-wrestling rock-paper-scissors minigames add randomness
WWE 2K15 leans a little harder on optimization, though the gap is small.
TNA Impact!
Move-chain knowledge runs out of depth quickly
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.