When watched on the new 4K TVs, the Netflix and Amazon streams are using the new HEVC compressed streams. At high bandwidth settings, you are getting something like 4x the picture quality than you get with DirecTV. The HEVC stream at 2x DirecTV bandwidth plus 2x more compressed by HEVC itself, yields that 4x improvement. By far, the best HD pictures on my UHD TV are those that come in over ethernet or wifi and processed by the hardware HEVC decoder.
For the record, DirecTV has the best picture quality of Cable or Satellite, and it is going to be a struggle for them to keep up with the quality of IP TV. The obvious next gen for TV is going to be all the channels you subscribe to and watch being delivered the same way. This is where Verizon/FIOS, Google Fiber, and that level of ISP are going to be able to compete.