head to head
Grand Theft Auto V asks more than American Chopper, and the gap is reads.

Execution · Practiced Mastery
Licensed bike riding and building that asks little beyond basic handling.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.
American Chopper leans Execution (Practiced Mastery); Grand Theft Auto V leans Execution (Practiced Mastery).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
American Chopper
Bike handling on missions is the only real demand
Grand Theft Auto V
Driving and shooting demand decent inputs.
Grand Theft Auto V leans clearly harder on reads.
American Chopper
AI riders follow fixed lines
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Grand Theft Auto V leans a little harder on variance, though the gap is small.
American Chopper
Courses and missions are scripted
Grand Theft Auto V
Some mission and lobby randomness.
Grand Theft Auto V leans a little harder on optimization, though the gap is small.
American Chopper
Chopper part choices matter, but shallowly
Grand Theft Auto V
Heists, money loops, builds 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.