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

Optimization · Pure Optimization
Stacking multi-class abilities and CT tricks to dominate tactically scripted encounters.

Optimization · Pure Optimization
A deep 3.5E optimization puzzle where prestige class chaining and feat synergies determine party effectiveness.
Fell Seal: Arbiter's Mark leans Optimization (Pure Optimization); Neverwinter Nights 2 leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Fell Seal: Arbiter's Mark
Turn-based; no timing windows whatsoever
Neverwinter Nights 2
Tactical pause negates twitch; positioning is deliberate not reactive
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Fell Seal: Arbiter's Mark
Enemy AI is scripted; fixed job archetypes behave predictably
Neverwinter Nights 2
Companion AI and enemy scripting are fixed, non-adaptive routines
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Fell Seal: Arbiter's Mark
Random encounters and loot add mild variance; counter procs are minor
Neverwinter Nights 2
Hidden enemy stat blocks and variable dungeon RNG create unknowns
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Fell Seal: Arbiter's Mark
Multi-class ability transfers and CT manipulation make this near-FFT optimization depth
Neverwinter Nights 2
3.5E feat synergies and prestige class planning define optimal builds
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.