head to head
Baku Baku asks more than FlatOut: Ultimate Carnage, and the gap is optimization.

Execution · Practiced Mastery
A competitive falling-block puzzle testing fast placement and combo chaining.

Execution · Pure Mechanics
Keeping speed through destruction-racing chaos that punishes clean-lap plans.
Baku Baku leans Execution (Practiced Mastery); FlatOut: Ultimate Carnage 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.
Baku Baku
Fast block placement under accelerating drop is the lead skill
FlatOut: Ultimate Carnage
Holding racing lines through wrecks and ragdoll chaos tests hands
Baku Baku leans a little harder on reads, though the gap is small.
Baku Baku
Versus play has light read of opponent pace
FlatOut: Ultimate Carnage
Rival drivers ram predictably, light multiplayer jockeying
Baku Baku leans a little harder on variance, though the gap is small.
Baku Baku
Falling animal/food order is random but bounded
FlatOut: Ultimate Carnage
Debris and pileups scramble any planned lap
Baku Baku leans clearly harder on optimization.
Baku Baku
Matching animals to food efficiently chains optimal combos
FlatOut: Ultimate Carnage
Car upgrades and track shortcuts are mappable
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.