I agree with Altamira 100%
I don't view an InReach to be a replacement for a PLB. Likewise, a PLB can't do everything an InReach can do.
Here is why I recommend a PLB over an InReach for if the SHTF ...
For those who don't know, an InReach is a satellite based two-way texting device that also has an SOS feature. You can communicate with the wives on shore, communicate with other boats when you don't want to broadcast information on an open VHF channel, get the weather, other features. It is subscription based (though I'm not sure if the SOS feature requires an active subscription). It uses rechargeable batteries that, depending on the device, last from as little as a few hours to as much as several days.
A PLB does one thing and one thing only, but it does it amazingly well. It transmits your GPS location via satellite communication to land-based emergency response agency, i.e., the US Coast Guard. It has a secondary feature which is to transmit a homing beacon via radio frequency so that once rescuers are in your general vicinity, they can close in on your position quickly. You only pull out the PLB when you are ready to call in the cavalry. It uses non-rechargeable batteries with a stated shelf-life which you need to send back to the manufacturer every few years for replacement. The batteries will transmit the emergency signal for a minimum of 24 hours.
In the real world, I see InReach devices in cup holders and on cell phone trays near the helm stations of boats. The owner has it out and about because of the several purposes that it fulfills, e.g., texting. If the boat would suddenly capsize or if the owner of the InReach should suddenly find themselves in the water, chances are, they are not going to have their device available to them.
In contrast, PLB is always stowed (in a pants pocket or on a belt) and always ready in an emergency.
My analogy for this is that the InReach is like a garden hose but a PLB is like that fire house behind the glass that says "break glass in case of emergency. You can use a garden hose for many applications and sure you can use it to put out a fire. But in an emergency, that fire hose behind the glass is always there ready to go.
If money were not object I would own both and have a subscription for my InReach. I would use the InReach to communicate and as a backup emergency locator device but I would still keep my PLB on my person at all times when operating offshore.
