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.

Optimization · Practiced Mastery
Refined loot shooter with skill-tree builds.

Execution · Practiced Mastery
40k co-op horde shooter with class builds.
Borderlands 3 leans Optimization (Practiced Mastery); Warhammer 40,000: Darktide leans Execution (Practiced Mastery).
Warhammer 40,000: Darktide leans a little harder on execution, though the gap is small.
Borderlands 3
Tighter gunplay than predecessors
Warhammer 40,000: Darktide
Melee-gunplay weaving under horde pressure
Warhammer 40,000: Darktide leans a little harder on reads, though the gap is small.
Borderlands 3
Enemies scripted, no adaptive opponent
Warhammer 40,000: Darktide
Scripted specials, not adaptive opponents
Borderlands 3 leans a little harder on variance, though the gap is small.
Borderlands 3
Weapon rolls and anointments randomize
Warhammer 40,000: Darktide
Director spawns and weapon rolls vary
Borderlands 3 leans a little harder on optimization, though the gap is small.
Borderlands 3
Skill trees, anointments, gear math deep
Warhammer 40,000: Darktide
Talent trees and breakpoints heavily solved
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.