A lot depends on what you are trying to do. Blasting 60+ down a desert road requires something very different than singletrack. One needs narrow focusing. HID still rules here. Those expensive Trailtech lights mentioned earlier by Ken are HID and cone in a very narrow focus that LED can't match. They are really nice. LED is catching up though and tend to work better on the slower trails. I've done the LPNF trails and they are great at night. To me less focused light works well as you can't usually see farther than 100 feet anyhow.
Those eBay LEDs over state the light a lot. Most of these use the Cree XM-L led. At best it can do about 1000 lumens at maximum drive. It takes good cooling and precise circuitry to do that, and those cheap lights have neither. Lights also have losses. Most real world results will have more like 700 lumens per XM-L led at best. That eBay light above is more like 2000 lumens. Still a lot of light though since most stock bikes are more like 400 lumens.
While the less expensive light can work well there is a big difference in build quality. The BD and TT stuff is well made, but you pay big time for it.
I've learned that redundancy is a good thing to have while riding at night. I've had a few failures over the years and I was glad that I had backups.
Even a $15 cheap XM-L flashlight and some tape can get give you surprising results.
Not narrow enough? This is a $110 model(4 bulb 3600 lumens). Im getting the $70 half model of this. (2 bulb 1800 lumens)
The Tree is 250ft from the light