If you come across in an emergency, the system is set up to prefer the use of telephones. Dialing 911 from a land line will give the dispatchers your street address. Dialing 911 from a cell phone will give them your latitude and longitude. If, for whatever reason, you cannot speak, they will know there is something wrong and know where you are. They will dispatch someone.
The entire E-911 system is set up around this, and that's the way PSAP's prefer you contact them.
If your cell phone/land line doesn't work, then sure, use the radio, but understand the limitations:
-There is no guarantee someone will answer.
-If someone does answer, they're no guarantee they'll assist.
-If they do assist, you'll need to give them accurate location data. May not be easy if you are unfamiliar with where you are, or are in a high stress situation. Also assume that someone well outside the immediate area will have no idea of the location, and it will take them additional time to reach the correct dispatch center.
The benefit to devices like InReach, PLB's, EPRIBS and Spot devices is that it's a one button push, it includes a number of useful pieces of information, including GPS derived latitude and longitude. The trigger sends the information to those that are trained to assist and know how to get help to you as quickly as possible.
Making it easy for the first responders to find you should be your highest goal.