There are many antennas out there which bear the HD label, Of course when they slap those two letters on the box the price goes up.. NOW in one case. I know of a store that sells two identical APPEARING antennas one of which says HD on it and costs more... However the antennas are quite a bit different.. NOTE they have sold these same two antennas (just without the HD label) for several decades, and the better one has always cost more.
But here are facts:
AN outdoor antenna will generally outperform indoor antennas, and a designed antenna will generally outperform a pair of rabbit ears or a single monopole. (Even with a tin-foil flag on it).
Next, the higher the frequency the more the following statement applies: HEIGHT IS MIGHT.. I prove this often..
Most mornings I check into the Breakfast Club net or Before Breakfast Club Net, these are on 75 meters (That is a long wavelength).. Now with a 100 watt transmitter and around 82 feet of wire I talk to a good portion of the US. I'm in SC and routinely hear and am heard by stations in Michigan, NYC, Idho, Texas, and many states in between. Fun sitting here in teh 40's listening to the temps in Madison, WISC I can tell you. No line of sight of course, the long wavelengths bounce around a lot.
I also operate on 2 meters (Between TV channels six and 7) NO way am I getting that kind of range.. But on 2 meters one day I had a new (At the time) radio, it put out 1 watt in hand held mode into a very poor antenna, I'd say about a quarter watt effective radiated power. Well, I tuned around (it was the first tuneable handheld) and found a repeater in Adrian, MI (I was in Detroit) and some hams in Toledo OH chatting.. A Ham from Windsor (I could actually see his house from where I was standing) tried to join in and .. did not make it.. I was able to relay... He was running about 40 watts effective at 30 feet as I recall.. I'm running 1/4 watt hand held......250 feet up in a skyscraper's tower.
HEIGHT IS MIGHT.
ANd the outside antenna is higher.
Finally... Though many stations did change frequency.. The new transmission freqauency is still in the old television band.. (Many VHF stations now transmit on UHF, but not all)
For example.. Chan 7 Detroit is, I believe using Chan 41.. Chan 2 Detroit is now using Chan 7 as their carrier frequency.
Chan 7 where I am for the winter.. Really is chan 7,, But Chan 4 is thirty something.
NOTE that the carrier frequency is one of the old channel frequencies, those did not change.. So the same VHF/UHF antenna that worked for ANALOG, still works for DIGITAL. The only major difference ....
IF I was designing today I would likely not include VHF-Low band (2-6) In my design, I'd design for 7 and above.. There are very few TV transmission on VHF-Low any more. (Still a few, but dang few)