Do some research on the subject. A radar gun throws a much wider path of waves and your detector can pick it up much easier when he's shooting anywhere near you. A laser gun is very narrow beam and you will not pick it up unless he's aimed directly at you. In a big SUV, it might not even pick it up if he does shoot you, depending on where you have it mounted. Laser needs a relatively flat, reflective surface to get a reading, which mean cops generally aim at your headlight or front plate area. If you have the detector mounted high on your windshield or visor, there's a chance it won't pick it up (it's that small of a beam). Mount it low and center on your windshield.
Speedracer has the right idea. I run the SR7 laser diffusers front and rear, in conjunction with my built-in SRX system in the Viper. In the H2, I've just got my old 8500, as it rare that I'm too much above the speed limit in it.