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 · Pure Mechanics
Tests off-road handling and freeform route choice across an enormous open map.

Execution · Practiced Mastery
Cornering execution over memorisable circuits, with light prediction in wheel-to-wheel multiplayer.
Fuel leans Execution (Pure Mechanics); Grid 2 leans Execution (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Fuel
Off-road vehicle control through weather events is the core test
Grid 2
Car control through corners is the entire moment-to-moment test
Grid 2 leans a little harder on reads, though the gap is small.
Fuel
AI racers rubber-band on scripts; online is thin
Grid 2
Online wheel-to-wheel adds light positional prediction
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Fuel
The huge map is scripted-but-unknown until explored
Grid 2
Tracks are fixed and fully visible
Grid 2 leans a little harder on optimization, though the gap is small.
Fuel
Route choice across open terrain rewards planning
Grid 2
Racing lines, braking points and car selection are studyable
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.