I will do a summary of the differences between DISH, DirectTV HD and SD other than channel line up and price
Starting with DirecTV SD:
DirecTV SD (Standard Definition or NTSC) for most customers uses one satellite, located at 101Degrees west longitude (When we speak of satellite numbers, without letters, we are normally giving 1/3 of their physical location, the Longitude, the other 2/3's are zero degrees latitude (Over the equator) and the proper altitude for geo-sync oribit, about 1/8 light second)
Thus a dual LNB antenna (One lens or "hockey puck" 2 coax outs) can either directly run two receivers, or via a switch several receivers. This makes it the best for RVers as it is easiest to set up, VU-Cube or most Dome type rooftop antennas work very well with this type of system.
Next is DISHnetwork SD: This uses TWO birds, one at 110 and one at 119 for most customers. Now, here is the problem, to get two birds at one time you need a TWIN LNB antenna (Means 2 lenses or hockey pucks) such as the dish 500
Some dome units can change address fast enough to satisify ONE dish receiver, but if you are running duals and one of you wants a show on 110 and the other wants a show on 119.. No joy.
Dish type antennas though (Either a
Motosat: Advanced Mobile Satellite Systems rooftop or a ground mounted tripod) can feed multiple receivers no problem.
DishNetwork HD uses 3 birds, See above comments
DirecHDTV uses 2 bands.. NO dome that I know of can get the 2nd band at this time so a DISH type antenna is required. Your Winegard portable wont' do the 2nd band either (They also use 3 or 5 birds, not sure as they are dumping 2 of the birds they were leasing from their competition)
So that's the basics
DirecTV standard is the simpliest choice for US customers.
Now: from here it gets complex... For example if you choose DISH and want a digital video recorder so you can record now and watch later.... You get one of the best DVR's on the market, dual inputs mean you can record two shows at one time (or watch two shows on different televisions) and dual outputs means you can WATCH one show recorded or live, while your "other" watches another, also recorded or live.
DirecTV's can record 2 at a time, but can only display one. Plus where as the DISH user interface is based on the Replay TV, (Even if TiVo sued 'em for it) Direct's R-15 is supposed to have the WORST UI in the business. (I believe it)
I will be running DVR's when I go back to Direct,,, but not Direct's (I will use external DVR's)
Dome, Dish or ground mount: NOTE: You have chosen a ground mount so you can skip this.
Domes come in 2 types, IN-motion and Stationary, why anyone would buy a stationary I don't know. They suffer from greater rain fade and lower signal strength than a dish type antenna. However.. you can get 'em that record while you drive (Why I have a dome)
Dish antennas also come in 2 types. Roof top and ground mount. They have better foul weather performance, and greater gain, they can also see (Depending on the dish) Multiple birds needed for Dish Network or HD on both services without re-pointing every channel change. This makes them much better for all but DirecTV SD.
However all roof top antennas can be blocked by the evil signal eating tree.
Thus you need a ground mount for such occasions. I recommend adding an "A/B" coax switch in the LNB line,, A goes to the Roof up ABOVE and the B goes to a connector down BELOW, either in the Basement or on a Bulkhead or in my case under the hood on the Brake master cylinder Bracket (Get the idea. A/B)
I hope his helps... I need to boiler plate this