When I was in the 12 volt business, Clifford was the best alarm system. Long time ago so let me see what I can remember
DEI (Viper/Python/Sidewinder and any other exotic snake u can think of) bought Clifford at some point and not sure if that changed anything...
We only sold Clifford to newer cars with competent/savvy owners because they were a bit more complex and required good car battery. But it was a much more advanced and high end system and much more customizable They required more power to work though, and required power to start the car/ turn it off. Whereas with DEI systems, if u pulled power from the alarm system, car starts and alarm is off.
For example With Clifford, no power to unit = no car start and no turning it off. Cliffords had normally open starter kill, so no power = no starter. better against inexperienced car thieves, bad for owners with dead or weak car batteries lol
Also cliffords had more inputs and outputs, zones, etc. You could make a custom "code" sequence like press defogger + window switch 3 times to disarm if you lost a fob or wanted to valet it. Installers make a difference, we took long time to install by soldering, looping, and/or terminating wires, where other volume shops used taps and tape..we hide and blend, theres would fall in your lap when you drop the dash or peek underneath
No backup battery = most alarms useless normally closed starter kill = almost useless much older car/bad car battery/corroded terminals/bad installer= issues with system
Remember, no alarm can stop a flatbed tow truck or a determined/experienced and fast, smart thief or one with time and patience
For just being notified of foul play, damage or stealing of parts/accessories look for something with multiple input zones, separate shock and lift sensors, remote paging that actually works (extended range antenna, maybe wifi or 4G connectivity available by now lol) and get a backup battery and internal + external siren to make the thief deaf or annoyed.