head to head
Neither is harder. They score identically on all four axes, so the difference between them is in kind, not degree.

Execution · Practiced Mastery
A slower 2.5D Kirby built around mixing two copy abilities into inventive combo powers.

Execution · Practiced Mastery
A bite-sized 3D Mario that compresses Galaxy-style level design into linear handheld courses.
Kirby 64: The Crystal Shards leans Execution (Practiced Mastery); Super Mario 3D Land leans Execution (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Kirby 64: The Crystal Shards
Relaxed platforming, some tricky shard grabs
Super Mario 3D Land
3D jumps and special-world remixes need clean control
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Kirby 64: The Crystal Shards
Fully scripted enemies
Super Mario 3D Land
Scripted enemies and bosses only
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Kirby 64: The Crystal Shards
Shard hiding spots unknown only once
Super Mario 3D Land
Star coin locations hidden on first pass
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Kirby 64: The Crystal Shards
Power-combo crafting solves shard puzzles
Super Mario 3D Land
Star coin collection and power-up management 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.