the 1st
in 5 minutes very easy :eyebrowlift:
simple : 150
render time : 1.3 minutes
render : cycle
the 2nd
in 10 minutes not hard but need much time to render
simple : 230
render time : 20 minutes
render : cycle
It’s because Cycles has to allocate samples for all of the light sources rather than just one.
Each light source will take some samples away from the other, in some cases (like for weak sources), there are options to optimize the sampling to tell the engine to not waste samples on it.
In the second image, Cycles has to split the samples available between five light sources, therefore needing more of them to converge the image.