Here is my 2 cents even though I know 2 cents is practically worthless.
LED lighting will allow a plant to photosynthesize. It provides energy to a plant for growth. The best, and in my opinion ONLY practical use for LED growing, is with confined spaces where heat and ventilation is an issue. The bottom line is- it is possible to grow a plant to completion using only LED lights... fact. I think we all know that..
1. LED lights are way too expensive
2. Yield is typically substantially less than HID
what most HID growers fail to acknowledge is that LED grow lights do serve a practical purpose and do produce adequate results for those who use them correctly. If one only needs a small harvest to get by, and uses a 16" by 16" by 4ft grow space, LED is not a bad idea.
Again, this is only my 2 cents, LED has worked for me, temperatures are not a big issue, and for the amount of watts they draw, results have been more than adequate for me.