Greets,
You might find
this radar comparison interesting.
LIDAR, affectionately called Laser (which is actually infra-red), is the problem. You can tell if local law enforcement uses LIDAR by the fact they'll have it mounted on a tripod, and an officer will be standing behind it. The device looks like a video camera with two lenses.
Nothing on the market will detect LIDAR quickly enough to save you from ticket (well ... sort of. You may get lucky and detect LIDAR that was aimed at someone else's car, but the chances of that are very low). Typically, if your detector detects LIDAR (which it can and will), there's a very high likelihood it is informing you that you're about to get a ticket. There are "jammers" on the market, but their effectiveness, and legality, are open for debate.
Traditional radar on the other hand is what a detector will give you a really good chance against.
Pay attention to what is used typically in your area, and you'll know if a radar detector is worth your dime. If it's mostly LIDAR where you drive the most, it won't help a lot. If they still used traditional old-school radar, go for it.
BTW, most highway traps seem to use traditional radar. I've mostly noticed LIDAR in the city.
Best of luck!