Having a security alarm system for your home is a good idea. Having signs that advertise that you have an alarm system is a good idea----MAYBE!! Thieves are looking for an easy target, they will bypass your home if you have a sign publicizing that you have an alarm system, SOMETIMES. Having signs posted is a good time for the "less is more theory". When you have a sign that advertises the BRAND of alarm system, you have just told the thief how to disarm your system. The schematics of security alarm systems are available through many sources, and the professional thief will use these sources. One source is the internet, another is an employee of the alarm system company. Thieves will actually pay the employee for a copy of the schematic. Now the thief knows how to defeat your system.
The best way to deter a thief and make it more difficult for them to defeat your system is to use a GENERIC SIGN, like the sign on the right, the one on the left tells the thief which schematic he needs. I tell my clients to change the signs to generic.

This sign is no good!! This sign is better!!!!
*THE BRINKS SIGN IS USED TO ILLUSTRATE A POINT ONLY.
I don't know for sure which sign is best. The name-brand sign doesn't specify the model of the panel, but the system is probably monitored. The sign on the right is probably just a ruse and doesn't even have an a monitored alarm system. But, having eiher sign tells the burglar to find an easier target.