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.

Execution · Practiced Mastery
The sequel adding Horde mode to the campaign-plus-versus cover shooter formula.

Execution · Competitive PvP
A class-based shooter spin-off of the tower-defense series with PvP and co-op modes.
Gears of War 2 leans Execution (Practiced Mastery); Plants vs. Zombies: Battle for Neighborville leans Execution (Competitive PvP).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Gears of War 2
Gnasher battles and movement tech set the ceiling
Plants vs. Zombies: Battle for Neighborville
aim and movement in class-based shooter combat
Plants vs. Zombies: Battle for Neighborville leans a little harder on reads, though the gap is small.
Gears of War 2
Human opponents in versus drive prediction play
Plants vs. Zombies: Battle for Neighborville
predicting human opponents' pushes and flanks
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Gears of War 2
Horde spawns add mild randomness
Plants vs. Zombies: Battle for Neighborville
minor loot and spawn randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Gears of War 2
Power-weapon timing and positioning are solvable
Plants vs. Zombies: Battle for Neighborville
class builds and lane strategy are 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.