I have switched back and forth several times. I now have six which is now 8 tuners with ota and two Hoppers.
Dish by far has better SD quality. HD is the same.
The guide is so much better on Dish.
Before you switch go to a blockbuster store and try it out. Being able to find things on the guide is important and YES there still are SD channels you may want to watch someday.
Wouldn't happen most times, but for amc, the best thing that could have happened as far as I am concerned , is being dropped by dish. I had never watched a show on there, until I got to hearing about the walking dead because of the drop.
Called in, got my roku (thank you dish) and have watched ever since.
For me, in that particular situation , it was a win win.