Just curious. Just repaired a Kodak carousel projector with
a 300W bulb and wondered what the power requirement for
a lumen for lumen equivalent discharge lamp would be, or is
it just smps gives the edge. But then is there a problem with
smps supplying a filament lamp, in the way of thermal runaway

I think the technology is stagnant. Same goes for home movies
on film. There isn't sufficient need to improve the design.

Agreed. Slide projectors never got past tungsten-halogen lighting.

Discharge lamps would no doubt be more efficient. But... not only would you
have to correct for color balance, but the bulb would have to be "mated" to
the projector's optical system.