They give you a false sense of security. Sure they will "save" you from time to time. But get too comfy and any talented cop will nail you with instant on. I have better luck using common sense and Waze, especially on the interstate.
Complacency with anything will get you. Waze is useless in my area, as it's not a heavily used app, so what might be the only solution for you, isn't for some.
The radar detector I use is very advantageous for the several states I frequent, as well as being paired with their phone app can provide more than jus. It will updated based off other factors, traffic accidents, slow downs, etc. It's a another tool to use, just like any other feature in your car.
The older POP radar, or the newer I/O radar is quick, but if you're with multiple cars in the area the user still has to narrow down who the offender is. It's not as narrow as lidar, or laser which is able to target a specific car.