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.

Reads · Competitive PvP
A 3D arena fighter where extendable-arm punches curve mid-flight in PvP duels.

Execution · Competitive PvP
An anime fighting game testing execution and prediction against human opponents.
ARMS leans Reads (Competitive PvP); Yu Yu Hakusho: Ghost Files - Dark Tournament 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.
ARMS
Curving punches and dodge timing
Yu Yu Hakusho: Ghost Files - Dark Tournament
Combo timing and spacing matter in fast 2D fights
ARMS leans a little harder on reads, though the gap is small.
ARMS
Whiff-punish games against adapting humans
Yu Yu Hakusho: Ghost Files - Dark Tournament
Human versus opponents drives prediction of attacks and blocks
Yu Yu Hakusho: Ghost Files - Dark Tournament leans a little harder on variance, though the gap is small.
ARMS
Minor stage and item randomness
Yu Yu Hakusho: Ghost Files - Dark Tournament
Some card-mode RNG and matchup chaos
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
ARMS
Arm loadout counters and matchup study
Yu Yu Hakusho: Ghost Files - Dark Tournament
Character movesets and matchups reward study
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.