for a tram scene I tested emitters vs. lights and finally, I have some wishes for both.
Emitters - very nice solution, if they would kept in any situation (far away from camera and hidden by other objects; know problems). I think, emitters could be good for best quality. I'm very curious for enhancements. It could be nice to get a keyword like "single" to get an light effect on the front side only.
Lights - like my examples shows there some issues - light distributation and reflections are not like expected. Advantage of lights - the stay constant visible where emitters are "turned off". Best would be if speculars of lights could be disabled and only the lighting effect would be shown at reflections (like from emitters). A global advanced option could be a first step, since it's difficult to add extra options to the light UI (for example of Rhino).
I know it's Christmas in two days, so we could talk about it next year. I had some time today and so post it now.