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
A destruction-heavy racer where holding a line through flying debris is the core skill.

Execution · Pure Mechanics
A survival game whose difficulty comes from awkward physics-based hand control.
FlatOut leans Execution (Pure Mechanics); Hand Simulator: Survival leans Execution (Pure Mechanics).
Hand Simulator: Survival leans a little harder on execution, though the gap is small.
FlatOut
Car control through destructible chaos at speed
Hand Simulator: Survival
Clumsy fine motor control of hands is the whole joke
Hand Simulator: Survival leans a little harder on reads, though the gap is small.
FlatOut
AI racers don't adapt; multiplayer reads are shallow
Hand Simulator: Survival
Other players exist but combat is chaotic, not modeling
Hand Simulator: Survival leans a little harder on variance, though the gap is small.
FlatOut
Physics debris and crash chaos inject randomness
Hand Simulator: Survival
Physics chaos and spawns create unpredictable situations
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
FlatOut
Lines, upgrades, and nitro management are learnable
Hand Simulator: Survival
Crafting and survival systems reward some planning
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.