What's "best"?
We have four Salvo/LM 21W HID lights. I like them. The Brightstar bulbs are pretty durable, and the lights are very bright and well-focused. We get 5 hours of burn time off the LiIon batteries we have in two of them. The drawbacks of HID are that they don't tolerate being turned on and off a lot, and you can't run them long outside of the water, and the bulbs have a shorter lifespan (although we've been getting in the neighborhood of five years from a bulb, which doesn't upset me much.)
A lot of friends are going to the LED lights. So far, I haven't seen one that compared in brightness or focus to the HID. But they tolerate being turned on and off and can be run in air, and the LEDs will last far longer than the HID bulbs. And the biggest advantage is that they don't involve a ballast, and most of our light failures (that haven't been due to Anderson connectors or wires) have been ballast failures.
Brand? I have LM lights. Other folks have Halcyon, and are happy with them. I know a few people who have Green Force, but they've never taken off around here. I saw a MetalSub light in the water a couple of months ago that was pretty impressive, although I would have liked to have had my HID for a true comparison. There are a lot of light brands out there now.