head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is reads, and it is a single point.

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

Optimization · Practiced Mastery
A PSP prequel following three keyblade wielders with a deep command-melding build system.
Darksiders leans Execution (Practiced Mastery); Kingdom Hearts Birth by Sleep leans Optimization (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Darksiders
combo-driven combat with dodge timing
Kingdom Hearts Birth by Sleep
Dodge timing against brutal secret bosses
Kingdom Hearts Birth by Sleep leans a little harder on reads, though the gap is small.
Darksiders
enemies are scripted
Kingdom Hearts Birth by Sleep
Pattern-based bosses, no adaptation
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
Kingdom Hearts Birth by Sleep
Command melding outcomes are documented
Kingdom Hearts Birth by Sleep leans a little harder on optimization, though the gap is small.
Darksiders
Zelda-style dungeons and upgrade routing
Kingdom Hearts Birth by Sleep
Command deck melding largely solves the game
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.