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

Execution · Competitive PvP
A PvP fighter where players smack an accelerating ball at each other until someone dies.

Reads · Competitive PvP
Minimalist fencing duel that is almost entirely about out-guessing one human.
Lethal League leans Execution (Competitive PvP); Nidhogg leans Reads (Competitive PvP).
Lethal League leans a little harder on execution, though the gap is small.
Lethal League
Hitting a ball at absurd speeds demands frame-tight timing
Nidhogg
Sword-height changes and dive-kicks need quick hands
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Lethal League
Human duels hinge on baiting and predicting swings
Nidhogg
Pure human duels of feints and conditioning
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Lethal League
Ball physics are deterministic
Nidhogg
Symmetric deterministic arenas
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Lethal League
Small movesets, light character knowledge layer
Nidhogg
Small toolkit, little to solve beyond fundamentals
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.