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 · Competitive PvP
An arcade wrestling fighter testing move timing and reading human opponents.
WWE 2K15 leans Execution (Competitive PvP); WWF In Your House leans Execution (Competitive PvP).
WWF In Your House leans a little harder on execution, though the gap is small.
WWE 2K15
Reversal timing windows decide most exchanges
WWF In Your House
Timing strikes and special-move inputs decides 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
WWF In Your House
Human opponents can be read in multiplayer brawls
WWF In Your House leans a little harder on variance, though the gap is small.
WWE 2K15
Chain-wrestling rock-paper-scissors minigames add randomness
WWF In Your House
Some randomness in move outcomes
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
WWE 2K15
Move sets, stamina and match pacing are learnable systems
WWF In Your House
Knowing finisher setups and combos underpins wins
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.