Cornell box comparison : PovRay vs. YafaRay vs. Kerkythea

[micheus]

I already noticed that when used POV-Ray in the past. For closeups of glass or metal I used to subdivide the object before to export producing small squares then the result is better.
But, it was a good catch to check if would work for triangular faces.

That seems to be related to a more common observation: The Shadow Line Artifact

Notice that even in the Yafaray render we still can see a slight squared look.
I also prefer the ceiling reflection on the lens on the POV image. The Yararay one looks a little blurred/greyed.

Maybe this article about Radiosity in POV-Ray can be of your interest.