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

Execution · Grand Arena
Build-fight battle royale with deep mechanics.

Execution · Competitive PvP
Aim duels against human crews layered over hidden-information loot gambles and extraction timing.
Fortnite leans Execution (Grand Arena); Marathon 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.
Fortnite
Build-edit-aim combos punish slow hands
Marathon
Gunfights against other crews reward raw aim heavily
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Fortnite
Box fights are pure adaptive mind games
Marathon
Predicting human crews' rotations and ambushes is constant
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Fortnite
Loot drops, storm, item rotations vary
Marathon
Loot spawns and unseen squads create hidden information
Fortnite leans a little harder on optimization, though the gap is small.
Fortnite
Loadouts, mats economy, rotations solvable
Marathon
Loadout economics and extraction routing sit underneath
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.