Most of the time there difference of price exists so do you withdraw bitcoins from one exchange and sell at higher rate exchange?
I don't, I only use one exchanger to easy to control my balance, one exchanger is enough for me because I have trading skills, I can easily earn profits with my skills.
it is good that if you are focused in one exchange and make things work,i do personally use multiple exchanges and use arbitrary trading when ever i find an opportunity to make some extra dough ,so i do use multiple exchanges all the time and being an alt coin trader i have to use all the exchanges.
The good thing for focusing on one exchange is you would not have any worries regarding to your arbitrage withdrawal on certain site, But you would surely miss the oppurtunity of buying on lowest price per exchange so the main thing here if you want to do multiple trade on certain exchange is to select those great exchange wich have good volumes on their alt trades.