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.

Optimization · Pure Optimization
Open-ended puzzles testing vocabulary-driven creative problem-solving more than any reflex.

Optimization · Pure Optimization
Coordinating three characters through fixed object-logic puzzles.
Scribblenauts Unlimited leans Optimization (Pure Optimization); The Cave leans Optimization (Pure Optimization).
The Cave leans a little harder on execution, though the gap is small.
Scribblenauts Unlimited
Typing words is the only physical demand
The Cave
Undemanding platforming with no timing pressure
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Scribblenauts Unlimited
Puzzle NPCs are static requests, not minds
The Cave
No adversary - a narrating cave is not a mind
The Cave leans a little harder on variance, though the gap is small.
Scribblenauts Unlimited
Puzzles are visible; nothing meaningful is hidden
The Cave
Each character's section is unknown on first descent
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Scribblenauts Unlimited
Finding objects that satisfy puzzle constraints is creative problem-solving
The Cave
Three-character object-shuffling puzzles are the whole 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.