@jda from LS? Long time!
I wanted to add my experience with this comparison from having my reef up for almost 20 years. I'm a 400w Radium and mag ballast guy for all the reasons above. However, 2 years ago I switched from 3 of them in Lumenarc reflectors over a 220g to two Reefbreeders LEDs for a few reasons. I calculated a $40/month savings in electricity from the light ($480 per year), $80/month savings in the summer from no longer needing to lower my A/C temp to keep the tank cool (with fans) and run it for a longer season ($320 per year), don't need to buy 3x 400w Radiums at $70 each ($210 per year), replace about 1 ballast per year $150. So I'm saving a little of $1100 each year. Minus $700 fixture... you get the idea.
Also, I was getting tired of trimming the SPS away from the glass and the local shops can only trade so many of these mini-colonies I would chop off, I was tired of cleaning off the inside of the reflectors, I wanted a more streamlined look (I don't use a canopy), and I kind of wanted to see what the LED fuss was about.
Skip forward a few years. The LEDs still look great on top of the tank, the color is pretty good, I don't have to trim corals every few weeks. BUT, I have lost all of my millis, several chalices off the bottom, my basketball size hammer has shriveled up to half the size, my colonies no longer encrust so their foundation becomes weak when the top portion continues to branch, I have lost every yellow and red SPS I had. I'm going to try some Gen5 Radions when they come out since they are supposed to be miles ahead of LEDs from a few years ago. I might pick up some G4 before then, so we'll see how it goes.