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

Optimization · Pure Optimization
A physics puzzle game about building wobbly towers and bridges from living goo balls.

Optimization · Pure Optimization
A minimal physics puzzle about chaining explosions to reach the goal.
World of Goo leans Optimization (Pure Optimization); Zup! X 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.
World of Goo
Placing goo balls needs only mild precision
Zup! X
Minimal dexterity to trigger explosions
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
World of Goo
No opponent exists
Zup! X
Solo - no opponent to model
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
World of Goo
Physics are visible and deterministic
Zup! X
Deterministic physics puzzles, no hidden randomness
World of Goo leans a little harder on optimization, though the gap is small.
World of Goo
Tower structure and goo economy are solvable per level
Zup! X
Finding the right explosion sequence is the puzzle
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.