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

Execution · Practiced Mastery
Arena duels mixing twitch dodge-punish play with RPG build preparation.

Execution · Practiced Mastery
A team shooter where aim and positioning against human opponents controls the map.
Dissidia Final Fantasy leans Execution (Practiced Mastery); 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.
Dissidia Final Fantasy
Aerial dashes, dodge timing and punishes demand fast hands
Splatoon 2
aim and movement decide ink battles
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Dissidia Final Fantasy
Human duels hinge on baiting bravery attacks and dodges
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.
Dissidia Final Fantasy
Some equipment and summon randomness, mostly known state
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.
Dissidia Final Fantasy
Builds, accessories and matchup knowledge shape every duel
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.