Another factor in favor of LED's vs. HID's is the expected life of the "bulbs." Though LED headlights are a fairly recent development, LED's themselves have been used for years. LED's are expected to last 10-20 times longer than HID's and even more than that compared to halogens. Even if you keep the car 10 years, you'll likely never have to replace the headlight "bulbs." LED's do dim a bit with age, but at a slower rate than either HID's or halogens. I had a car with HID's that had a bulb burn out after about three years. It cost about $500 to replace, given the cost of the bulb and the fact the bumper had to be removed to access it. Over the next few years I'd guess LED's will probably replace both halogens and HID's in all but the cheapest vehicles.
HID (or Xenon) headlights are different from the latest LED headlights. Although the brightness is similar, but it takes about 30 seconds to let HID light growing to its full brightness oppose to instant full brightness on LED. Thus flashing the hi-beam becomes a problem on Bi-Xenon headlights but not on LED low/high beam headlights. The hard-to-find AFS will automatically level your headlights up and down based on load and turn headlights left and right based on your steering wheel angle. Even on popular Lexus RX350 you can only pay extra to get HID headlights and auto leveling only system. Porsche Cayman offers only HID, no LED yet.