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

Optimization · Pure Optimization
Grid-based dungeon crawler about riddles, secret buttons, and square-dancing around monsters.

Optimization · Pure Optimization
A grid dungeon crawler testing build choices, puzzle-solving and enemy-type counterplay.
Legend of Grimrock leans Optimization (Pure Optimization); Vaporum leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Legend of Grimrock
Real-time grid strafing around slow monsters
Vaporum
Real-time grid-dancing around enemies needs some timing
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Legend of Grimrock
Monsters chase on simple fixed logic
Vaporum
Enemies follow fixed behaviours per type
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Legend of Grimrock
Secrets hidden until found, then fixed
Vaporum
Dungeon is authored; loot mostly placed
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Legend of Grimrock
Party builds, riddles, and pressure-plate puzzles dominate
Vaporum
Gear loadouts, rig builds and puzzle solutions are the core
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.