Nigel Calder has an extremely good article on
new marine lighting technology in the latest
issue of "Professional Boatbuilder" magazine.
One of his goals is to compare the utility of
various technologies for various tasks. Doing
this is tricky, but he spends a lot of time
explaining the units involved so that one can
at least understand why oranges and apples
are not directly comparable. he also spends
some time comparing efficacy of light sources
(pretty much "efficiency" if you mean "light
output per watt").

anyway, it's great Calder writing, remarkably
well-done research, and boiled-down so that
one can come away with some understanding
of the "shape" of the problem space.

as for ProBoat, if you are really interested
in boats, even if you don't intend to build
one yourself, i recommend it most highly.
it costs a few bucks, but is full of information
you won't find anywhere else and written by
people who really understand their stuff.

-mo