Chromecast for Sling

I was told by a person at Sling TV that roku had the least problems. I bought a Chromecast and the picture seems to "downgrade" more than when I had my roku 2 that's dead now hooked up. I have plenty of internet speed and everytime I try to change the speed settings in the Sling app it auto resets to "best" My picture will "downgrade" for lack of a better word and then in a few minutes look good again. And I generally don't run more than 1 device at a time through my modem. Any thoughts?…

Chromecast for Sling