A ratio is a ratio is a ratio. Look at all of the equations on torque multiplication and you will see that it all has to do with ratio, not the size of the numbers involved. A 4:1 ratio with a 100 spur and 25 pinion is the same as a 4:1 ratio with an 80 spur and 20 pinion. N0 matter how you change the number of teeth in the equation, with a 4:1 ratio the motor will spin 4 times for each revolution of the spur.
To keep it simple, yes, the larger spur has a longer lever so it takes less force to make it move. But since the pinion has a longer lever also, it has less power to make the other lever move. These two items cancel each other out in the equations.
As has been stated, the biggest effect any of this has is in weight placement. The motor is one of the heaviest components on any of our cars. Moving it .25 inches can have a big effect on balance.