Hi my name's Movin On, and I've been working in the field of car audio and mobile electronics for over 8 years. I've installed everything from navigation systems, to full car stereo systems, remote starters, alarms and beyond. To learn more, visit our website at www.movinon.com.
When purchasing a radar detector, you must first understand that they're two different types of radar detectors--dash-mounted radar detectors and integrated radar detectors. Both have advantages and disadvantages. A dash mounted radar detector plugs into your cigarette lighter and suction cups to your windshield. The advantage of this is it can be quickly put away, and not easily stolen. Also, you can put it into another car if you're using a different car. If you have multiple vehicles, this may be the way to go.
Integrated units are mounted on the front bumper, rear bumper, and inside the grill and usually feature a laser diffuser. A laser diffuser will actually make it so that laser shots cannot read your speed. Now eventually they may read your speed by buy that time you will have slowed down. You also want to check your local laws for laser and radar to make sure that you're following them when you buy one of these detectors.
A lot of dash mounted radar detectors and integrative radar detectors feature GPS marking that can warn you of red light cameras and speed traps. These are very useful if you live in the suburbs or if you live in the city, as radar isn't typically used on residential roads. The GPS monitors the location of the vehicle and it queries a database of all these locations. If you see a location that's not in the database, you can flag it and it'll be shared with other users.
It's your responsibility to insure the legality of radar detectors and laser diffusers in your area. The police stay up-to-date with radar detector technology and they're always trying to make sure that their radar guns somehow surpass the radar detectors. So a lot of times what you're paying for is the more updated technology that's gonna stay on top of what law enforcement is using.