head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is variance, and it is a single point.

Execution · Competitive PvP
Stick-skill football against human opponents whose habits must be read.

Execution · Competitive PvP
Stick precision and constant prediction of a human opponent's tactical habits.
FIFA Soccer 13 leans Execution (Competitive PvP); Pro Evolution Soccer 2015 leans Execution (Competitive PvP).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
FIFA Soccer 13
Ball control and finishing inputs decide moments
Pro Evolution Soccer 2015
First touch, through-ball timing and finishing demand precise sticks
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
FIFA Soccer 13
Online humans keep adjusting their patterns
Pro Evolution Soccer 2015
Human opponents bait, switch tactics and punish habits
FIFA Soccer 13 leans a little harder on variance, though the gap is small.
FIFA Soccer 13
First-touch randomness and deflections add chaos
Pro Evolution Soccer 2015
Deflections and referee calls add bounded chaos
Pro Evolution Soccer 2015 leans a little harder on optimization, though the gap is small.
FIFA Soccer 13
Tactics and squad setup are a studied layer
Pro Evolution Soccer 2015
Formations, player roles and set pieces reward study
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.