First up warranty. If you didn’t get a warranty you likely have the wrong one.
Technical side is also pretty clear cut simple as the rules are much the same as the old analog days.
These 3 antenna look the same to most people but can result in very different results. The available signal in “perfect conditions” can be just fine but only on clear sky hot days or stormy weather can we see how well they perform as the usable signal level is naturaly reduced it will only be still working with the best choice.
Length of the small horizontal elements if not matched to the correct frequency will reduce signal level and increase noise level. Same deal with old and new. Analog and digital. The simple rule that does apply to all wireless communication: Shorter elements higher frequency/Longer elements lower frequency.
The length of the boom or longest part of the antenna is where forward gain is found. This gain is the same deal with old and new antennas. Digital and analog. Old rules apply here much the same small low gain for metro/city/high signal areas and larger high gain antennas for rural and low power transmitters.
Phased arrays are not a new thing. They have been around since world wars and are not the best choice in all locations but do have an edge in difficult areas where ghosting on analog was an issue and drop outs on digital was an issue.
Like old like new there is cheap junk and their is known quality brands. Often using the cheapest “square one” because its “square” and “that’s digital” results can be the same as their old antenna or even worse.
The above photos show what happens after just a few years after install of the cheap antenna. Parts bend and fall off. Your TV signal will still work great until a bit of bad weather or hot summers day raises the noise level.
Installers may relate the damage to bad weather or birds even when the last antenna was in place for 20 years with no such issue. This is like replacing your cars windscreen with a plastic bad and blaming the wind for it flapping. The antenna is designed to be out in the weather or it is designed to be replaced on a regular basis.
If you have the best of everything and confirmed correct this doesn’t mean it will simply work. Products need to be installed correctly for optimum results. Antennas and their masting should be installed to manufactures and Australian standards. If not installed correctly results could be the same as cheap or old antennas and water ingress resulting in property damage is possible.
The last difference is related to safety. Previously large antennas needed a fair attention to detail and secure mounting practice for reliable long term results. More recently the use of very small masts often hidden less care may be given to building attachment. For the safety of not the installer but the general public in and around the location. In Tea Gardens and Hawks Nest a number of antennas have been found to be installed with silicone only. These would of only needed minor attention to improve signal but have resulted in reinstall for safety reasons. With no warranty you really do not know what you are getting, in these cases additional cost to the owner and a work safe re-portable issue is raised.