Bittrex is a great option, although the transaction fee is higher than poloniex but fast web technology and good support
Exchanges do matter but you dont have to cater for them when you are starting your trading, as this thread is all about starting thread so I think it is quite better to go for learning rather than just jumping off to next stages. Bittrex better but firstly you have to know how to trade and how to earn. Then exchanging will come.