This is a great discussion! Excellent points on many issues I have had questions on.
I am currently leaning towards LEDs in my application due to the heat reduction - less need for more heat management strategies, I have been impressed with the developments in the last 2 years especially. I first tested an LED light in 2009 and it was pretty pathetic. Now they are giving a good savings on not just the light energy, but also the supporting infrastructure needed and energy required. Maybe not as high in yield, but getting increasingly close.
However I am seeing increasingly the ceramic metal halides on the market using 315w-630w range. How do these new developments fit into the equation?