Power density might be lower but these have a much narrower beam profile about 20 degrees fwhm so you can couple more usable light.
I also looked up the rebel green, 180 lumen at 700ma 160 degree emission. My green has most of it's light coming out at 20 degrees and puts out 2000 lumen. It would take 11.1 rebels to equal the output of this at about 7.7 amps. Heat sinking that many rebels is also a pain.
Don't get me wrong luxeon stuff is great but they each have their place. These were initially designed to provide light for video projectors.
Chad
When the going gets weird, the weird turn pro.