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

Execution · Grand Arena
A football sim where reading opponents and precise execution both decide matches.

Execution · Practiced Mastery
A team shooter where aim and positioning against human opponents controls the map.
FIFA 20 leans Execution (Grand Arena); Splatoon 2 leans Execution (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
FIFA 20
precise passing, dribbling, and shot timing
Splatoon 2
aim and movement decide ink battles
FIFA 20 leans a little harder on reads, though the gap is small.
FIFA 20
reading human opponent tactics live
Splatoon 2
predicting human opponent positioning
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
FIFA 20
minor ball physics and injury randomness
Splatoon 2
weapon and map rotation randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
FIFA 20
formations and player builds solvable
Splatoon 2
loadout and turf strategy solvable
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.