Emissive planes will almost always take longer to converge than spotlights, because iRay "understands" spotlights and has special processing for them. Had I been lighting that scene, I'd have used spots on at least the ceiling. You can make them have significant area, and widen their "spread angle" if you need to - works pretty well.
The other thing you have to watch out for with emissive planes is shadows. If you drop in big ones, because they aren't at all directional, you can get washed out images without shadows that look "wrong" to the eye, but it's hard to say why. The scene shown doesn't really have that problem - the fact that the emissive planes are small and spaced out does give you shadow effects - it's just something to know.
Personally, I use spots wherever I can, since they tend to perform better. I only use emissive planes as ghost lights (i.e. with an opacity of like 0.00001) when I need to illuminate something from an angle where the spotlight would be visible. For example, if someone's in a car and are too dark compared to the background, I might put a ghost light where the windshield is to better illuminate inside.
But, back to the question in the OP: Personally, I adjust the lighting, as required, for each scene. For some well-lit scenes this isn't necessary - you can move characters around and they're still well-lit. But I don't have the slightest problem with fiddling with spotlight locations on a scene-by-scene basic if I need to. Obviously, you try no to make dramatic differences so that it's obvious you've done so, but I'll frequently have "background spots" (like the overhead ones in the sample scene) that handle most of the illumination, and then one or two "character spots" that I use to make sure the characters are well lit. The latter I'll move around to follow the characters as required. Kind of like the fact that they'll light the set in a play, but then may have a spot that follows an actor around to make sure they stand out a bit.
Bottom line - it all depends on the scene and what you're trying to accomplish.