I didn't read all the posts on this thread yet, so I apologize if what I'm going to say is redundant, but here's my take on the original post:
There are quite a few brands of LED lightbulbs out there now...but, for the most part, the ones that are fairly reasonably priced, are the 9.5 watt (equivalent to a 60 watt incandescent) bulbs. So, those are the ones I will refer to hereafter in this post...
From what I can tell, most of them are either a 2700K (warm white) and a 5000K (daylight) temp.
Convenience is the advantage to any bulb because everyone (almost) knows how to screw in a bulb!
Availability is another advantage to LED and CFL bulbs...You can get them anywhere! Even the grocery stores sell them! If one goes bad, it's not a panic to replace it.
Ok...that being said....The light-globe of an LED bulb doesn't get hot so the bulb can actually be placed extremely close to the plant -which is great for seedlings and small plants! A 23 watt CFL bulb in the same application, would fry the seedling in minutes because the twist of the CFL gets
very warm. However, back the CFL off the plant a bit, and the plant will love the warmth.
I went to Ace Hardware one rainy day....saw a drip-pan made for catching the oil when you change the oil in your car and bought a couple of them to be inverted and used as reflectors....Then I ordered a couple 4-bulb light sockets online...drilled a hole in the center of the drip pans, attached the 4-bulb sockets to the pans, spliced a couple of old extension cords...drilled a couple more holes to attach some clips to hang them...voila!
I can mix and match the LEDs to get a "full-spectrum white" and place them right on top of the plants without overheating...and due to the fact that the orientation of the lightbulbs is horizontal, the direction of the light is focused and almost encapsulated by the drip-pan reflectors so the intensity is pretty good, I think. Of course, the intensity will drop incredibly-fast when you back the fixture off even a few inches.
BTW, a bulb-fixture like this, also enables me to add UV bulbs if I want....or any other kind/color of bulb that I might want to mess with! And I can also hang them, on-end, along the inside walls of my tent to add side-lighting.
I think the drip pans cost about $10 dollars apiece...the bulbs I bought in those four-packs that go on sale all the time (one pack of each color)...I don't remember what the price was each, but it was under $10 for the 4-pack...The extension cords and electrician's tape I already had...the 4-bulb sockets were under $5 dollars each...So these fixtures were cheap and easy-to-make.