I have no experience with jammers. Couldn't tell you if they work or not. I'd love to test a laser jammer though, just out of curiousity. If I run across anybody that has a laser jammer and is willing to let me try to clock them I'll sign out a LIDAR unit and try it.
I've never owned a detector but I've seen plenty of them sitting on the dash while I'm getting license and insurance info from the driver. One guy actually asked if he could step out of the car once. I said sure... He gets out, snatches the detector from the dash and proceeds to stomp it into pieces on the roadway.
Detectors work as far as detecting the signal and letting you know but they really only give you a heads up if you don't see the popo before it goes off. Usually, if you're not paying attention and your first warning is the detector, it's too late and your speed is sitting in the window of the radar/LIDAR unit. Again, when I was assigned to working traffic I wrote a LOT of speeding tickets to folks with detectors.
I think they may save a few folks in a few instances but for the most part I think they are a huge waste of money. Knowing where and when to speed and just playing it smart will probably save you more tickets than a detector. If anyone asks me which detector is best I tell them to buy from whichever company it is that guarantees to pay your fine. At least that way you get something for your money.
I put detectors and jammers (until proven otherwise) into the "too good to be true" category. A small black box that you can stick on your ride and just speed away to your heart's content as long as you slow down when it screams at you? I'm waiting for some company to put out a device that they tell you will cloak you with a force field that makes you and your ride invisible to all others. Ummmm, ok.
One last note. If you do get tagged and pulled for speeding and you have a visible detector, you will, with almost 100% certainty get cited. It's like showing an intent to break the law and most popo that I know NEVER cut slack for detector owners.