Why do people like saying what they did not know anything about..
See the way u are just condemning their exchanger and sincerely speaking is a lie from the pit of hell.
I have been using poloniex as well as bittrex u mentioned but why saying what u are not sure of?
I use poloniex every day and nothing like withdrawal issue there maybe ur friend never know how to use poloniex.
Tell him/her to PM me for more information