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 · Practiced Mastery
Zelda-meets-God-of-War action adventure starring the horseman War.

Optimization · Practiced Mastery
An action-command RPG where dodging and countering boss tells is half the battle.
Darksiders leans Execution (Practiced Mastery); Mario & Luigi: Bowser's Inside Story leans Optimization (Practiced Mastery).
Darksiders leans a little harder on execution, though the gap is small.
Darksiders
combo-driven combat with dodge timing
Mario & Luigi: Bowser's Inside Story
Every attack and dodge is a timed action command.
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Darksiders
enemies are scripted
Mario & Luigi: Bowser's Inside Story
Boss tells are fixed and learnable.
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Darksiders
world and bosses are fixed
Mario & Luigi: Bowser's Inside Story
Little randomness beyond minor drops.
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Darksiders
Zelda-style dungeons and upgrade routing
Mario & Luigi: Bowser's Inside Story
Badges, gear, and learning attack patterns close fights.
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.