These wallets are just integrated with shapeshift.io.  When you're exchanging between coins in your Exodus or Jaxx wallet, you're using shapeshift.io.

Shapeshift are not very transparent with their fees - they claim to have none, but the exchange rate varies.  I just compared the Ether-Bitcoin exchange rate from Shapeshift (on quick setting) and Coinmarketcap, and I found that the Shapeshift rate was about 0.4% higher.  By comparison, Bittrex rates are 0.2%.

Personally, I'm happy using Shapeshift for small amounts, but I would prefer to use an exchange for larger amounts because of the liquidity and, arguably, lower fees when doing it in bulk.