head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Execution · Competitive PvP
Football execution and human mind-games layered over tactical formation play.

Execution · Competitive PvP
Execution on the ball plus constant prediction of the other player's shape.
International Superstar Soccer Pro 98 leans Execution (Competitive PvP); Pro Evolution Soccer 2009 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.
International Superstar Soccer Pro 98
First-touch timing and finishing demand practiced hands
Pro Evolution Soccer 2009
Close control and finishing windows demand stick precision
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
International Superstar Soccer Pro 98
Versus matches hinge on outguessing a human defender
Pro Evolution Soccer 2009
Online and couch opponents adjust tactics against you
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
International Superstar Soccer Pro 98
Bounces and deflections add bounded match chaos
Pro Evolution Soccer 2009
Ricochets and keeper parries add small randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
International Superstar Soccer Pro 98
Formations and set-piece routines have learnable best answers
Pro Evolution Soccer 2009
Squad setup and tactical sliders reward preparation
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.