On one hand, if you have an alarm the odds of your home being successfully burglarized when you're not at home is incredibly low. As long as you remember to turn it on every time you leave. I responded to a few houses where I swear they just broke an out of the way window to see if the cops showed up, or did a quick smash-and-grab if they could see something worthwhile in easy reach. Make sure your alarm panel isn't visible from outside your home, but most importantly don't forget to set it every time.
On the other hand (and what the alarm companies don't tell you) is that the police don't come running code when your residential alarm goes off. If your police force has a reasonable response time for most calls, then they'll probably get there in a reasonable amount of time if your alarm goes off under normal circumstances. After a storm when there are twenty other burglar alarms in the city going off, plus downed trees, traffic signals out, several car crashes and such you may end up at the bottom of the priorities list. That's after a storm. Imagine if the power was out for any length of time, or the phone lines were down, or what might happen in the case of civil unrest. What will you do then? The cops are going to be busy.