Polo is the best exchange by far. Those who are complete newbies or used wrong codes to transfer their funds should be banned for inability to operate on crypto exchanges. I happily doubled my money in polo. It is the most reliable one I know of. I use other exchanges only to get the unique coins
I generally do not understand what a difference can be between one and the other resources. As for me, then with the help of one and the other you can trade without any problems. Although there may be some system limitations, But this is the individual approach of each user.
You must be right. I'm also holding account in these two exchanges and I'm not facing any problems with them. Sometimes I face delay with poloniex for processing my withdrawal, but other than that there was no notable difficulties I faced with them. I rarely do tarde at Bittex, so for they are also good with their execution time and trading volumes.