Light is a thief's enemy. It seems too simple, but they will usually find another victim of your place is either well lit, or equipped with motion lights. They know you don't always see them when the light comes on, but they also know the light means someone might be alerted by it, whether it's you, your dog, or a neighbor. I have motion lights on all sides of my home that are solar powered. They cost nothing to use, and most the time I simply see critters when they come on. But I have seen the occasional person run off when I checked to see why one was on. So I feel better knowing the crook will be lit up when he approaches my home.

In my experience, light is not much of a deterrent during the prime lowlife activity hours after midnight to 5 AM    Additional response is required; a minimum of a barking dog or other loud noise.  

I considered making an automated device that poked a barrel or pair of them out in a highly noticeable location when the alarm was triggered.  I was afraid if the police ever did respond to one of the many prowler calls, they might trigger it and that could provoke a stun grenade / tear gas attack on the house when the mechanical device did not respond to their commands.