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
Keeping speed through destruction-racing chaos that punishes clean-lap plans.

Execution · Pure Mechanics
An arcade test of jump timing and enemy-flipping precision on a single screen.
FlatOut: Ultimate Carnage leans Execution (Pure Mechanics); Mario Bros. leans Execution (Pure Mechanics).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
FlatOut: Ultimate Carnage
Holding racing lines through wrecks and ragdoll chaos tests hands
Mario Bros.
Precise jumps and bump timing under crowding enemies decide survival
FlatOut: Ultimate Carnage leans a little harder on reads, though the gap is small.
FlatOut: Ultimate Carnage
Rival drivers ram predictably, light multiplayer jockeying
Mario Bros.
Versus mode adds light human interference, enemies are scripted
FlatOut: Ultimate Carnage leans a little harder on variance, though the gap is small.
FlatOut: Ultimate Carnage
Debris and pileups scramble any planned lap
Mario Bros.
Enemy spawns vary slightly but patterns are quickly learned
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
FlatOut: Ultimate Carnage
Car upgrades and track shortcuts are mappable
Mario Bros.
POW block usage and enemy routing have known best lines
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.