You have to look at each device you are looking at (whether dedicated device, or something like an apple watch, or whatever else) and understand how it works, and what it will do if it detects a fall and you don't respond. Also what your options are for calling for help yourself if you can (e.g. hitting a button, dialing a phone, yelling for Alexa, or whatever). Not all emergencies where you want help and can't walk across the room involve a fall. Heart attack, stroke, etc might be a good time to have a button handy you could push.
I would definitely want a device that can call for help if there is a fall and the person that fell is not able to confirm to someone, somehow that they are still OK. (Details of how to say "I'm OK" will vary by device.)
Basically, figure out which scenarios you worry about most, and pick one or more devices that might help you (or your loved one) in that situation. None of these devices are perfect in every possible situation. But one or more of them could detect a fall and get you some sort of help if you needed it, at least some of the time. Better than nothing, hopefully.
You have to do some research about what is available in your area. Consider cell signal strength, wifi availability, landline availability, and which services require cell vs wifi vs landline, etc. Consider if you're looking for protection inside the home, in the home and yard, or in the home and around town, etc. Look at what companies offer services in your area, and what you want from a device.
For our family:
For me, relatively younger, the emergency features on an apple watch that has cellular and wifi connectivity are good enough for peace of mind for now, and gives me coverage at home as well as when I am out and about.
For my older parents it was a Philips lifeline pendant for each of them. That particular system required a landline, which they still have at their home (not everyone can still get a landline, and other systems from Philips and others work without a landline). The pendants worked in the home and yard, and would detect a fall automatically (most of the time) and also had a button that could be pressed for any reason (not limited to falls). When activated by a fall or a button press, a voice would come over the base unit. If you tell them you're OK, they say have a nice day. If you don't reply, or say you need help, they send help. Their house required two base units so they could communicate with the base from anywhere in the house. If they were to fall in the yard, they would not be able to hear the voice from the base unit (or vice versa), so help would have been called whether they were OK or not, though that never happened.
For most elders I personally know - big resistance to any dedicated device ("I don't want to wear that thing") combined with lack of basic tech knowledge (apple watch and similar things are not usable solutions) means they don't have anything, and they just plan on not falling or needing to call for help unexpectedly. Don't let indecision lead you or your family member to be the one lying on the floor unable to call for help. Pick something and learn how to use it/teach them how to use it.
cj