Every couple weeks someone comes in trying to build an led light to save them money from the overpriced professional rigs. The first thing I always ask is what's your background in electronics? Basically if you know how to build, wire, solder and work with electronics. It's definitely doable. If you can't you'll spend more on supplies and gear than just buying the video light to begin with.
Most camera lighting you're going to want a flood anyways, unless you're doing night time telephoto which will never look good anyways. But I say your best bet is simply making a flashlight rig using inexpensive lights. But if you want to illuminate things with that nice diffused professional look. Led's simply can not provide enough light economically or efficiently. HID is the best way to go.
The advantage with HID is you can get a high powered system really cheaply. 2x55 watts of HID car lights can be had for $50 or so. These also are most efficient at 4300k which simulates daytime sunlight on camera the best. The most efficient led's are in the 6000-8000k range which will look too blue on camera and you'll need gels which kill the efficiency even further. Then you still need a soft box to diffuse the light even more to prevent shiny faces and glare, again more light loss.
HID's come with their own ballast and aren't affected by heat. LED's you'll still need a heatsink, possibly a fan to cool them if you're driving them hard, then a driver, all of these cost money, and you'd better be good at electronics cause one mistake can set you back money and time. HID is plug and play.
I made some fun ghetto rigs that lit really well, completely portable with lithium battery packs I had from remote control cars. They were simply cheap tripod stands with umbrellas clamped to them painted silver. I tied the HID bulbs to the umbrella and they simply reflected a nice diffuse neutral light, and lots of it too, onto the subject, much more flattering than anything I could make with led's and for less money. Plus since I often was filming from a car I simply often just made an extension cord that took power from my car's trunk based subwoofer, the beauty of 12 volt systems, or if there was a plug, I had a computer power supply. Now that's convenience and flexibility.
