head to head
Neither is simply harder - they are hard in different places. Borderlands 2 demands more execution; Pokemon Stadium 2 demands more reads.

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

Optimization · Systems & Chaos
N64 arena battler where rental and imported Pokemon fight in 3D tournaments and mini-games.
Borderlands 2 leans Optimization (Systems & Chaos); Pokemon Stadium 2 leans Optimization (Systems & Chaos).
Borderlands 2 leans clearly harder on execution.
Borderlands 2
Aim matters but generous hit feel
Pokemon Stadium 2
Menu-driven turn battles; no physical demands
Pokemon Stadium 2 leans clearly harder on reads.
Borderlands 2
Enemies are scripted loot fodder
Pokemon Stadium 2
Human PvP cups reward prediction; AI cups are mappable
Borderlands 2 leans a little harder on variance, though the gap is small.
Borderlands 2
Procedurally generated weapon drops vary
Pokemon Stadium 2
Accuracy rolls, crits, rental rosters add randomness
Borderlands 2 leans a little harder on optimization, though the gap is small.
Borderlands 2
Skill trees and gear math heavily solved
Pokemon Stadium 2
Team building, movesets, type matchups are solvable
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.