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
Arcade racing with Mario Kart-style power-ups bolted onto licensed cars.

Execution · Twitch Chaos
Kart racing where drift skill fights against item-roll chaos on themed tracks.
Blur leans Execution (Pure Mechanics); Pac-Man World Rally leans Execution (Twitch Chaos).
Blur leans a little harder on execution, though the gap is small.
Blur
Racing lines and dodging shots demand car control
Pac-Man World Rally
Drift timing and shortcut jumps decide clean laps
Blur leans a little harder on reads, though the gap is small.
Blur
Human racers bait and time power-ups against you
Pac-Man World Rally
Human races add light item-timing prediction
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Blur
Power-up pickups and incoming attacks add chaos
Pac-Man World Rally
Item rolls scramble positions every race
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Blur
Track knowledge and pickup routes are learnable
Pac-Man World Rally
Track shortcuts and kart picks are learnable edges
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.