I am biased towards DEI alarms based on experience, not so much on preference.
overe th past few years i have installed many alarms (college job).. out of all the alarms that i worked with, i would say DEI makes the highest quality, least problematic alarms.
we installed more DEI alarms than anything else.. and still the other brands had more problems.
for instance, Alpine makes alarms.. they are a great Head Unit maker.. but that is where it stops.. the alarms they make are very problematic, and they offer little support to customers... every alpine alarm we ever installed didnt work quite right and many times we ended up swapping them out for a different brand... it was unfortunate because alpine remotes looked cool (thats why many people bought them)
just one example.