For a video projector system where the illumination is directed down a
mirrored light tunnel onto the active silicon DLP or whatever , I wonder how
much light is wasted from a mercury arc source and a reflector. The ones
I've seen the area of the colour wheel / light tunnel is perhaps 10 percent
of the open aperture end of the reflector and as the bulb is not a point
source perhaps only something like 10 percent is used.
With a bank of LEDs the directionality is ideal , you can mount on the
surcace of a sphere and direct them all , individually , at the wanted area.