HD is harder to pick up than SD.....
Well.. Once perhaps. Here is the major difference customized for DircTV.
SD uses one bird, Located at 101W,,, So you need to set Elevation and Azimuth and there you are.. Simply what.
HD uses 3 Birds, 99-101-103 and (you do not need to know this the antenna designer does) the 99 and 103 birds are in a different frequency band.
Back to what you need to know.
So you have to set Elevation TILT and azimuth That is 3 parameters and thy interact some what. (Generally you pre-set Tilt and leave alone but not always)
This also means no DOME can get Direc HDTV (At least the RV domes, Marine domes are different) so yes it is "Harder"
Same for DISH.
Dish SD uses two birds 110 and 119, HD adds a 3rd.. Other than having the proper antenna.. Set up is nearly identical But with a SINGLE receiver,, Some DOMES will work.
In all cases the proper Ground/Tripod mount antenna will work, Multiple Receivers/DVR's HD/SD/ Dish or Direc.. IF you have the right antenna, properly set it works.