@Ceciliabr

Is it the more advanced ray-tracing in Sunflow that makes it perform slower than YafaRay in your test?

YafaRay is primarily optimized to work with Blender but offers a lot of nice features as shown here.
The purpose of my contribution to this new plug-in is to help find general settings for a rendering approaching or equivalent to that of Sunflow. Duration is an additional indication.

To return to your question, it is the YafaRay "Path Tracing" global illumination settings that make a similar rendering (regardless of shininess) faster than Sunflow.

I hope that Puybaret will be more successful than me in the implementation of area lights or caustic photons which are also important features.