Although I don't have any advise on which detectors are better than others, I will say that radar detectors are not all they are cracked up to be.

If you are cruising down the highway and a speed check is set up, your radar detector is useless, as by the time your detector is beeping, the officer probably already got you. When cops are sitting and waiting for speeders, they will usually shut off their radar in between shots, that way your detector won't detect them. The only thing radar detectors are good for is those rural roads where a cop might try to get you while driving towards you. Since he is driving, he doesn't really have time to turn the radar on and off, therefore he is constantly emitting radar and your detector will pick him up.

I've gotten two speeding tickets, both with the use of a radar detector, both on interstates at speed checks. The detector did save me several times while driving back roads.

Furthermore, even though many detectors sense laser as well as radar, your chances of detecting laser soon enough is pretty slim.