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
Tactical grid combat plus studio management, both solvable with planning.

Optimization · Pure Optimization
Lane defense classic about managing a sun economy against shambling waves.
Chroma Squad leans Optimization (Pure Optimization); Plants vs. Zombies leans Optimization (Pure Optimization).
Plants vs. Zombies leans a little harder on execution, though the gap is small.
Chroma Squad
Turn-based commands, no dexterity involved
Plants vs. Zombies
Clicking to plant, minimal pressure
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Chroma Squad
Enemy AI follows simple mappable rules
Plants vs. Zombies
Zombie waves follow set compositions
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Chroma Squad
Hit rolls and episode events add modest noise
Plants vs. Zombies
Wave timing and lane pressure vary mildly
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Chroma Squad
Studio economy, crafting and teamwork combos are the puzzle
Plants vs. Zombies
Sun economy and lane setups are near-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.