I have used both, a lot, and it depends on many factors, up to 500w with the right fork, front is " ok " but for your setup, go with a rear motor..
Be aware that most hub setups will be freewheel only ( thread on type ) and that the rims are generally centered on the hubs and not dished for strenght reasons.. some hubs are built properly with an offset at teh axle, some are not... look into an eZee from ebikes.ca imo..