I have been using led lights on my reef tank for about 4 yrs now. A nice mix of royal blue, red, cyan, and neutral white. The color achieved via blending these spectrum's is great for growing corals and appealing to the eye as well. And in the past 4 yrs I have moved on throughout my house and installed led lights in most fixtures. In regular lights it's the lens that makes the difference, giving you a better spread or a more narrow beam depending on which one you choose. The nice thing about led's is when coupled with a backup power supply like solar power I can still run my coral reef tank during a power outage pretty easy as it doesn't require the same amount of power metal halides would require. The same holds true for my pumps they are all low voltage as well. I have a few lights in my house I leave on 24/7 because they are led and burn only 4 watts but put out the brightness of a 40watt bulb.

You can also hack a burnt out cfl bulb, depending on how many led's, add a mini driver or resistor to the led's to handle AC voltage and you have a screw in led bulb. Alot of work for just one bulb so after all said and done i'm sure it wouldn't as effecient than just buying one, more along the line's of an experiment or class project imo.

I think the catch with these are the equivalent wattages

12 watts, equivalent to a 100-watt incandescent bulb.

Philips best is 17 watts equivalent to 74-watt, so the efficiency is a bit better.

Mine is my house are 6w (32w), seems bright enough but then I have multiples in each room.