I have had several and the best type to have is the GPS model that has static speed cameras in their database updatable. There may not be many (fixed cameras) in the US at the moment, but they're coming!
As for laser detection, I have not yet found one that will detect a police hand held laser gun or a laser driven camera before you are "in the beam". To avoid false alarms you can tailor the laser detection zone but this inevitably puts your dash mounted detector out of the radar "cone" which is usually targeted on the number plate. So, always fit a detector with a remote sensor.
THE most effective method is the radar beam "reflector" sometimes called a jammer, and these things really work. They simply reflect an aimed beam back at the gun which gets an "error" message and does not record any speed, but be warned, in the UK, if you are found with one you are liable to be charged with "obstructing the Police in the pursuit of their duties"