I noticed such a big discrepancy today on the exchange rates that are being offered on different sites which allow you to withdraw to your bank account. I just had to take some screen shots to show you the prices so you can make an informed decision when deciding which service to use.
So for instance lets dream and say I have 1 bitcoin on Bittrex and I want to withdraw it to my bank account. If I send it to Coinbase I am going to get $2,571.68 but if I send it to Coinjar I am going to get $2,627.33 - A whopping $55.65 more!
The best thing to do is shop around at the different sites you can use and see who is offering the best rate at the moment. I'm not sure if there is always such a large difference but I will be keeping an eye on it.
These screenshots were all taken within a few seconds of each other, so there was not much time for price fluctuation.
Bittrex BTC/USD
Coinbase BTC/USD
Coinjar BTC/USD
