- Rear wheel install = power to push forward, will be affected by gear change
- Front wheel install = power to pull forward, gears remains unchanged
.....- might not pull as well, since the weight is mostly on the rear, so it might be losing power to torque.
Rear (and front) hub motors are unaffected by changing the bicycle gears. "Bottom bracket motors" like Cyclone are the only ones that get better torque or speed depending on what gear you choose. The amount of torque and power are not affected by whether it's a front or rear wheel motor.
Most of the time it won't matter whether you use front wheel drive or rear wheel drive, but...
If you want the bike to have relatively even weight distribution (which gives better handling) you want to avoid batteries and motor on the back (or batteries and motor on the front).
Traction will be better with a rear motor, but it'll only matter in really extreme offroad type riding or on snow/ice.