RG6 is the one to use, and is currently used by all cable and satellite companies I have ever run into. I saw one installation done with RG59 by a company that was used to running video for cameras.

RG6 is better than RG59 at running high frequencies, such as satellite signals, for long distances. All cables work better at low frequencies than at high frequencies, and it turns out that the thicker the cable, the better it is at the high frequencies. RG11, though, is around a half inch thick, VERY hard to bend, so not at all physically suited for home use. It's the stuff you might see running from pole to pole for cable distribution.

Quad can mean either of two things: quad cable or quad switch. A quad switch allows a dish to feed four satellite receivers. When there was only one (DirecTV) satellite, its LNB had two outputs. Those could be fed into a quad switch, which then gave four outputs. "Which kind of quad" could mean that. The current Phase III dishes have a multiswitch built into them, so they already have four outputs that can go to different receivers. But you can expand that with a 4x8 or 5x8 (the fifth input is for antenna or cable); four inputs are from the dish, and there are eight outputs.

There is also quad cable. Cable has, at minimum, a foil shield covered by a braid for keeping signals broadcast over the air from leaking into it. This is called dual shield, because each of those things is a shield. Quad is, starting at the foam core, foil, braid, foil, braid, outer cover. Four shields. Quad.

Quad is better than dual shield at keeping out interference. However, the need for the improvement is dubious in most setups. I installed and antenna system in a retail store about four miles from all the transmitting towers in the Los Angeles area, about as close as you can be while not up on the mountain, feeding about 450 TVs and some 40 FM receivers. I used RG59 and had zero interference.

In my experience, the definite reason for me to use Quad shield is so that no other installer, or smart-ass friend who doesn't really know the facts, can look at a client's installation and say "oh, he think this through enough to put in the really good stuff, did he?" Cable companies are rightly paranoid about signals both getting into their cables and leaking out, so their universal use of RG6 makes sense; it just ensures that amateur installers (most cable guys) are more likely not to cause problems.

By the way, about interference -- to be interference, it has to be on the same frequency. To get interference on your satellite cable, you would have to be within a half mile or so of somebody using 950 mHz to 1450 mHz, just above the top of the broadcast TV spectrum. This is highly unlikely.