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

Optimization · Pure Optimization
Lane defense classic about managing a sun economy against shambling waves.

Optimization · Pure Optimization
An economy and layout optimization puzzle about keeping a small simulated city solvent.
Plants vs. Zombies leans Optimization (Pure Optimization); SimCity 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.
Plants vs. Zombies
Clicking to plant, minimal pressure
SimCity
Pause-friendly building removes any physical test
SimCity leans a little harder on reads, though the gap is small.
Plants vs. Zombies
Zombie waves follow set compositions
SimCity
Region multiplayer is cooperative, not adversarial prediction
Plants vs. Zombies leans a little harder on variance, though the gap is small.
Plants vs. Zombies
Wave timing and lane pressure vary mildly
SimCity
Disasters and agent simulation quirks add mild randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Plants vs. Zombies
Sun economy and lane setups are near-solvable
SimCity
Zoning, traffic flow and specialisation economies 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.