head to head
Neither is simply harder - they are hard in different places. Borderlands 2 demands more execution; The Witcher: Adventure Game demands more reads.

Optimization · Systems & Chaos
Loot-shooter RPG built on gear chasing.

Variance · Systems & Chaos
A dice-and-cards board game testing quest routing against heavy draw luck.
Borderlands 2 leans Optimization (Systems & Chaos); The Witcher: Adventure Game leans Variance (Systems & Chaos).
Borderlands 2 leans clearly harder on execution.
Borderlands 2
Aim matters but generous hit feel
The Witcher: Adventure Game
Digital board game - clicks only
The Witcher: Adventure Game leans clearly harder on reads.
Borderlands 2
Enemies are scripted loot fodder
The Witcher: Adventure Game
Human rivals race and block, but interaction is shallow
The Witcher: Adventure Game leans a little harder on variance, though the gap is small.
Borderlands 2
Procedurally generated weapon drops vary
The Witcher: Adventure Game
Dice combat and event card draws dominate single quests
Borderlands 2 leans clearly harder on optimization.
Borderlands 2
Skill trees and gear math heavily solved
The Witcher: Adventure Game
Quest routing and risk-odds management reward planning
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.