Hmm I didnt know the new sentras had an electrical PS pump.
Pros, if you run an electrical water pump youll only run one belt and you will still have power steering. Less parasitic drag on the engine. Free up a marginal amount of hp/tq. Better throttle response (good for heel and toeing). You can have power steering with the engine off, although I dont know what good that will do. You can mount it where ever you like for better weight distribution.
Cons, getting it all set up. I really cant see cons to electric power steering. Maybe the amps the pump uses. If the pump fails you can still drive the car unlike an electric water pump.