Which sign is better to put outside the home for security
SIGN of home security system like ADT
Sign "No Tresspassing, Violators will be Shot"
Sign " owner is armed"

which one do you have on outside of your home ?
unless you have the services of ADT I do think you are allowed to use their sign
the other signs indicate that you have a gun and that could be good or bad any way you look at it
how about putting up motion lights, or some kind of warning system on the edge of your property like the electronic fences for dogs, you probably would be more comfortable with that than signs
I switched signs with a neighbor down the street. So anyone entering our home thinking they know how to beat one security system finds another instead. I also have a dog that barks.

The other two signs would only work if the criminal thought you might be home and pretty much awake.
None of those really do anything to stop a break in. All signs do is make you feel better.

An ADT sign will only work if you actually have the system. Then it is the system that works NOT the sign.
The home security system sign definitely. Modern technology is no match for the criminals of today.