Hey, I'm Xil's friend... And it depends what you're looking for. Certain radar detectors are better for police radar/laser protection, others are better for red light camera prevention... Some have good random features, others don't.
For the best police detection:
#1) Valentine V1.8 ... They have a V1.7, which I have, and it isn't that much worse, but it doesn't have a POP mode, which can be useful in areas where police use POP radar... Even though POP radar only gives an estimated speed and is excessively expensive, if they use it, expect a ticket even though they don't know your exact speed... It won't stop them. The one other downside to the 1.7 vs the 1.8 is that the 1.7's Ka band detection is just a bit weaker than the 1.8, or so I hear... But it's cheaper, and I'm cheap
#2) Here I'd say the Escort 9500ix, which is generally viewed as the best overall detector for various reasons, such as a GPS that detects common false alarms (such as grocery store doors), and it also warns against red light cameras, as well as just plain telling you the speed you're going digitally, which are all very nice features ... but hell, it's expensive and a lot of its features aren't really needed.
Research for yourself if you care beyond what I call the best the best:
Radar Detector Forums - Radar Detector Jammer Forum
Radar Detectors Reviews; Best Radar Detector
... And if you're looking for a good radar detector - cheaper than face price... Used that work fine:
eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices
... I got my Valentine V1.7 for $260 with free shipping. Not too shabby.