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 execution moderated by item randomness and learnable track routes.
Blur leans Execution (Pure Mechanics); Sonic & All-Stars Racing Transformed 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
Sonic & All-Stars Racing Transformed
Drift timing and transforming vehicle control reward practice
Blur leans a little harder on reads, though the gap is small.
Blur
Human racers bait and time power-ups against you
Sonic & All-Stars Racing Transformed
Human racers add light positional mind games
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
Sonic & All-Stars Racing Transformed
Item rolls regularly upend race positions
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
Sonic & All-Stars Racing Transformed
Track shortcuts and drift-boost routes 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.