Actually, only one of these qualifies as a true PLB--the last one. Unlike the others, it uses the Dept. of Defense satellite network and distress calls go directly to the Coast Guard (with which you register the PLB).

The other two are communication devices that use private satellite networks. If you "push the button" your call will go to that private company and then be forwarded to the area SAR. There have been incidents in which this has resulted in delays. While they do have an emergency function, basically they are devices to reassure your friends/family that you haven't fallen off a cliff or been eaten by bears.

With all three, if you "push the button," your contact person(s) will be called first to make sure that's you in the area from which the call is coming and to find out additional info such as itinerary, gear, etc--info you should have left with your contact person.

The DeLorme gadget will allow you to send and receive brief text messages, which the others don't. This could be very useful if there is an emergency because you can have 2-way communication with the SAR folks, let them know the nature of the emergency and possibly receive some first aid directions. The SPOT sends only a few preset messages and can't receive any, so it has no 2-way communication. The PLB just sends the emergency signal. Neither the SPOT nor a PLB can tell you whether or not the signal went through, although the PLB is far more reliable because of the satellite network it uses.

I plan to keep my PLB (McMurdo Fast Find) unless someone (like my son for when I have his kids with me) decides to purchase the DeLorme so we can send the parents text messages.

I suspect that for the anxious parents of your Scouts, the DeLorme might be the best, since it's the only one of the three with 2-way communication. Of course you may find once you're out there that the anxious parents are the last ones you want to hear from!

Most of the places I backpack have no cell phone coverage even at the trailhead, so I leave my cell phone turned off and hidden in the car.

There's obviously a story behind all this ("March 22….")! Do you care to share or would you rather not?

I suspect you'll find more on these gadgets in the "Backcountry Health and Safety" section. It's sort of a tossup as to which section is more appropriate!