To answer the above inquiry there are no preferred satellite/cable providers to work with any model of Slingbox. Slingbox is currently compatible with most cable/satellite/internet providers in there respective supported countries. The only thing to keep in mind is when using an satellite provider their remotes may be in RF which will cause issues with the virtual remote of the Slingbox working. Below I have an included an article in the event that you run into any of those issues.
Hope This Helps!!
Yes Sling boxes are built to work with any source of programming be it cable box, Satellite box, even over-the-air.
But it's true that the IR (infra-red) remote capability is mandatory for what you're watching.
I have a Dish box and use UHF (through the wall) remotes all over the house,
but I have an IR cable from the sling box to the DVR box
So the issues are proximity to the source(s) and IR conflicts between sources. because there's only one IR transmitter
coming out of the Slingbox with a "hydra' head for multiple sources. I have an older Slingbox HD 500?
It depends what kind of content you prefer. Some say Direct has better sports channels. I like Dish Network. It's more economical for me.