Since you are focused with BTC/USD tradind you will be solely using a web wallet. Coinbase will be the best choice for you, though this type of trading is risky and letting your coins sleep at them, put some of youe bitcoins on an electrum wallet for long term holding, it is secured.
Coinbase has major security issues. Trading is difficult enough. Hackers stealing your Bitcoins on a daily basis is too much for me.
I have just finished reading the article in Fortune.com (Hacking Coinbase: The Great Bitcoin Bank Robbery)
http://fortune.com/2017/08/22/bitcoin-coinbase-hack/Coinbase was successfully hacked 30 times in a month. That is an average of once a day. BTC-e is even worse.
And because Bitcoin is hard to trace, it means that the lost money won't be able to be recovered.