Hi everyone, I have a question for someone that can help me, I do not understand how come some people instead of using the default Blender lights (Point, Sun…) they use a Plane or more planes with an emission node in Cycles. Which one is better? Which one renders the better lighting on the objects?
Thanks in advance for your anxwers 
I prefer the lightsource based lights as they stay the same energy when scaling. I also think they get to a cleaner result faster. My main reasons to use mesh lights are when making tiny light sources like LEDs (MIS off) that don’t really contribute to scene lighting. I will of course also use them if I need to map them with an image (like for a LCD monitor) given they have UVs. I heard lightsources will get UVs, but that won’t help in this case because they are not camera visible. Given their ease of control, the lightsource ones are excellent for helping out GI for interiors, as I can’t afford waiting for a pure indirect solution to clear up (cove lights are a nightmare).
The downside is that for GI use you have to be really careful where you put them, since an area light is completely flat and won’t emit out to the sides, or a spotlight can’t have any energy directed in the opposite direction (you’d need two). In that sense there are lots of lights missing (cube, tube, pyramid, elliptical etc). None of them reacts properly to the is*** outputs of the Light Path node. You can check them for things like diffuse and glossy on the object level, but here the isSingular option is missing.
Trying to limit bounces also isn’t very intuitive, as emission and lightsources have different ways; Light sources have their object level max bounces setting, whereas for emission you have to mess around with the Light Path stuff. And then, they seem to react differently on the MIS setting.
I don’t know. I just find it kinda messy. I will usually try the lightsource first though.
Use whichever you need for the illusion, they all produce different outcomes. The point lamp will produce a large bulb or bloom and can be accentuated in post processing to an even higher degree. Emission objects should cover most of the scene though.