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
Retro international football sim with team management basics.

Execution · Competitive PvP
Reversal timing and pacing against an opponent baiting your counters.
Football International leans Execution (Competitive PvP); WWE 2K15 leans Execution (Competitive PvP).
Football International leans a little harder on execution, though the gap is small.
Football International
passing and shooting input precision
WWE 2K15
Reversal timing windows decide most exchanges
Football International leans a little harder on reads, though the gap is small.
Football International
reading human opponent's attacking patterns
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.
Football International
minor bounce and ref randomness
WWE 2K15
Chain-wrestling rock-paper-scissors minigames add randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Football International
formation and substitution strategy
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.