@ Toddster

In a case like this where an offscreen, flat light card is all I needed they could look identical(surface shader does not show in incandescence passes so if this were a visible light bulb that would be a problem). Overall the mia_light_surface allows for more control with less hassle, like in this case, I told it to only contribute to reflections and not to FG since I felt it would just throw the lighting off, surface shader has no option for that. You can also retain actual surface shading while having some self illumination by balancing the diffuse/additional color weights, the surface shader is flat all day everyday. Then there is the ability to link lights to the shader to control it's intensity, which is a huge boon if light intensities are animated, if not then it's one less attribute that needs to be adjusted constantly anyway. The surface shader could do this but it would require some expressions.

@ Ben Hobden

Yes, I can't see why not, it serves as a general base that you can build on. In the case of a car, I think you might end up using more light cards (overhead ones too) since there are more contours to highlight. Give it a go!