One thing I've come to recommend for upgrading to LED lighting - you should seriously consider changing the fixture.
Each lighting technology is different, and has it's own strengths and weaknesses. Putting an 'adapter' bulb in is just a non-optimal compromise, running the lighting technology in a way not best suited for it's strengths.
I'll do a brief rundown on the 'top 3':
Incandescent:
heat tolerant and indifferent to cold - you don't need to keep it cool(actually, hotter is better)
produces lots of heat - you need to insulate the fixture
Natural shape is a globe
Omnidirectional by nature
Relatively high failure rate, so a fixture where it's easy to change bulbs is best.
Doesn't require any support electronics
Dimming: pretty much any way you like, but becomes less energy efficient the more you turn it down.
Flourescent:
Not heat tolerant - A fixture that exhausts heat is best
doesn't like the cold.
doesn't produce lots of heat - much more efficient
Natural shape is a tube
Mostly omnidirectional. When in tube form it tends to distribute light better than a single globe
Lasts far longer, on average, than Incandescent(~10X). Ergo, more trouble when replacing lights is acceptable.
Does need electronics - seperate ballasts and bulbs is more economical in all but the smallest fixtures.
Dimming is complex.
LED
Not heat tolerant, but doesn't mind cold
Even more energy efficient than Flourescent, but still needs to dump it's heat.
Natural shape is a flat spot.
Functions most naturally as a flood.
Normally requires support electronics, though they are normally much simpler than a ballast for flourescent light. On the high end you have a current controlled power supply, on the bottom end a resister and enough LEDs to act as their own half-bridge rectifier.
Lifespan double that of even FL. At this point, considering the fixture part of the package isn't out of place.
Dimming: If designed to handle it, relatively straight forward, and the curve for energy:light is pretty much flat. Halve the energy = more than half the light(yes, they get more energy efficient the lower you run them).
Don't get me wrong, there are some great 'adapters' out there. But you're looking at increased expense and reduced efficiency by trying to fit an LED or FL into a fixture designed for Incandescent. You tend to 'insulate' Incandescent bulbs in order to keep them from burning nearby materials. You want to do the opposite with the other technologies. There's also the question of where the support electronics live - whether right by the light, or off a bit where they can radiate their own heat.
Taking a big fixture and stuffing a couple LED 'bulbs' in there is a compromise. I have a fixture with a cheap board with the LEDs mounted right on it. It cost less than buying LED bulbs for the old fixture. It has massive room to dissipate heat, the electronics are seperate from the LEDs, so the heat from both aren't piling up together, and it's taking advantage of LED directionality to throw all the light 'down' as opposed to up right into the fixture(where, if you're lucky, there's a reflector to direct the light back down again). Less waste.
