Our department has been using Niterider for some years. They seem to be the best compromise between cost and effectiveness. You can go way cheaper, but I've tested several inexpensive units and they are not effective at letting you see.
You can go way more expensive, as with the Cateye "stadium" light, but you're talking serious bucks. Kind of for the dedicated night trailrider or adventure racer.
The cheap LED lights do allow you to be SEEN, so if that's your primary consideration they're fine.
But if you want to be able to see where you're going, you need a bit more illumination. The model we buy has the dual lights, one high beam, one low, or both together. Battery life is OK, we find maybe an hour on high, and 2/12 on low. Like most batteries of this type, when they die, they die quick.
The units are well made and durable, and factory support is excellent. They switched a bunch of our older units over to the newer chargers and plug setups without charge.