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
Tests quick ball control and outguessing a human defender's tackles.

Execution · Competitive PvP
Sony's mascot brawler where only Super attacks score kills, making meter management the whole game.
International Superstar Soccer Deluxe leans Execution (Competitive PvP); PlayStation All-Stars Battle Royale 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 Deluxe
Pass and shot timing under pressure decide matches
PlayStation All-Stars Battle Royale
Combo routes into Super meter need decent but modest hands.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
International Superstar Soccer Deluxe
Versus a human, faking runs and reading tackles is central
PlayStation All-Stars Battle Royale
Super-only kills make baiting human opponents the core decision.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
International Superstar Soccer Deluxe
Deflections and keeper bounces add light chaos
PlayStation All-Stars Battle Royale
Items and four-player chaos add mild 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 Deluxe
Formations and set-piece routines are learnable systems
PlayStation All-Stars Battle Royale
Meter-build efficiency per character is the solvable layer.
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.
full breakdown
International Superstar Soccer Deluxe →
full breakdown
PlayStation All-Stars Battle Royale →