The only reasons you would buy an Over the air antenna is because you don't already have one.
Today's antennas are small,light weight and vary in ranges. Usually, they come in 30 mile 40 mile and 50 mile ranges but in my opinion You get more range with an older antenna
If you already have the steel, heavy, old style antennas, your grandfather used to use, installed on your roof, you don't need anything else Providing your television set was made after 2007.
You don't even need a digital converter box because these newer TVs have a digital tuner and software inside
Over-the-Air Broadcast hasn't changed since the invention of TV. The only thing that has changed is the What television stations offer. Alone side analog Broadcast signal it is also Digital
Don't be confused between the meaning of digital and high definition(720p,1080p). You can still receive a digital Channel but it can be in standard definition (480P)
Most of the major networks like CBS, NBC, ABC, and Fox are usually high definition widescreen broadcast
"Digital Television (DTV) is an advanced broadcasting technology that has transformed the television viewing experience. DTV enables broadcasters to offer television with better picture and sound quality, and multiple channels of programming. Since June 13, 2009, full-power television stations nationwide have been required to broadcast exclusively in a digital format.The switch from analog to digital broadcast television is known as the Digital Television Transition. In 1996, Congress authorized the distribution of an additional broadcast channel to every full-power TV station so that each station could launch a digital broadcast channel while simultaneously continuing analog broadcasting. Later, Congress set June 12, 2009 as the deadline for full power television stations to stop broadcasting analog signals." by FCC.Gov
The other advantage of using an antenna mounted on your house, or in your attic, brings over the service your cable company delivers is that the signal is uncompressed. The cable companies are delivering multiple services Cable TV, Telephone, and Internet, so they are forced to compress these signals in order to deliver them fast through a coax cable at the same time.
Uncompressed signals gives you beautiful Picture quality. When people see it live and for the first time they describe it as almost 3 dimensional.
The best part when using an antenna is that it's totally, Totally free
Watch the video below from my YouTube channel AskUncleDave for more about these old style antennas
Buy Tablo TV Tuner and DVR here
Buy Vizio TV Set in this Video here