head to head
Neither is simply harder - they are hard in different places. Sonic & All-Stars Racing Transformed demands more optimization; Stumble Guys demands more variance.

Execution · Twitch Chaos
Kart racing execution moderated by item randomness and learnable track routes.

Variance · Twitch Chaos
Timing jumps through physics chaos where crowd randomness outweighs mastery.
Sonic & All-Stars Racing Transformed leans Execution (Twitch Chaos); Stumble Guys leans Variance (Twitch Chaos).
Sonic & All-Stars Racing Transformed leans a little harder on execution, though the gap is small.
Sonic & All-Stars Racing Transformed
Drift timing and transforming vehicle control reward practice
Stumble Guys
Timing jumps through obstacle chaos is the main input
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Sonic & All-Stars Racing Transformed
Human racers add light positional mind games
Stumble Guys
Light jostling with humans, little true prediction
Stumble Guys leans clearly harder on variance.
Sonic & All-Stars Racing Transformed
Item rolls regularly upend race positions
Stumble Guys
Crowd physics and obstacle chaos randomize every round
Sonic & All-Stars Racing Transformed leans clearly harder on optimization.
Sonic & All-Stars Racing Transformed
Track shortcuts and drift-boost routes are learnable
Stumble Guys
Shallow route knowledge is mastered quickly
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.