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 · Practiced Mastery
Cornering execution over memorisable circuits, with light prediction in wheel-to-wheel multiplayer.

Execution · Pure Mechanics
High-speed anti-gravity handling over memorised racing lines with light weapon chaos.
Grid 2 leans Execution (Practiced Mastery); Wipeout 2048 leans Execution (Pure Mechanics).
Wipeout 2048 leans a little harder on execution, though the gap is small.
Grid 2
Car control through corners is the entire moment-to-moment test
Wipeout 2048
Pixel-perfect anti-grav handling at speed is the core test
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Grid 2
Online wheel-to-wheel adds light positional prediction
Wipeout 2048
Online racers add light weapon-timing prediction
Wipeout 2048 leans a little harder on variance, though the gap is small.
Grid 2
Tracks are fixed and fully visible
Wipeout 2048
Weapon pad pickups inject some racing randomness
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Grid 2
Racing lines, braking points and car selection are studyable
Wipeout 2048
Track lines, barrel-roll spots and ship choice are learnable
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.