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.

Execution · Pure Mechanics
WWII gunfight execution with light multiplayer prediction.

Execution · Pure Mechanics
Tests twitchy miniature car control and track memory amid party-weapon chaos.
Call of Duty 3 leans Execution (Pure Mechanics); Micro Machines V3 leans Execution (Pure Mechanics).
Micro Machines V3 leans a little harder on execution, though the gap is small.
Call of Duty 3
Aimbot trivialises both campaign and multiplayer gunfights
Micro Machines V3
Tiny cars on twisty tabletops punish every slip
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty 3
Multiplayer adds modest human positional prediction
Micro Machines V3
Couch rivals can be baited with weapons and nudges
Micro Machines V3 leans a little harder on variance, though the gap is small.
Call of Duty 3
Scripted setpieces and spawn flow add minor unknowns
Micro Machines V3
Pickup spawns and chaos shuffle close races
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Call of Duty 3
Map knowledge and weapon choice reward light study
Micro Machines V3
Track memorisation and shortcut lines pay off
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.