I don't know who we use. It isn't ADT or Brinks.
Bad side - ugly (small, but ugly) black boxes up in the corners of the ceiling, with little flashing red lights, the motion detectors. "Beep-beep-beep" every flipping time a door gets opened. Once in a while, someone will forget it is on and come out of their bedroom in the morning and forget to put their code in (and go downstairs), or open a window, and the whole house shrieks! That alarm is much worse than fire alarms.
Good side - I feel more secure when DH is out of town, which he is a lot. We live in a big house out in the middle of nowhere. I couldn scream my head off, nobody would ever hear it.