Are there any benefits to using PF motors instead of EV3 ones?
The cost of a PF motor is about one third of an EV3 motor.
If there is no need to regulate the motor, using PF motors is a way to save costs. Also PF motors are more compact.
Its possible with lego converter cables to attach them to an EV3, however the NXT to 9V cable is hard to come by. Ofcourse there are DIY solutions (soldering) or third party components.