This was actually an older project, but it worked for what I wanted to test. Typically I always use the mitchell-netravali filter as it seems a good mix between sharp and smooth. I've always found the cubic b-spline to be too soft, however I've always been curious how it would look with something rendered at a higher resolution... partly because there always seemed something slightly cartoonish about the mitchell-netravali filter even if I generally preferred it. I was also playing with soft shadow settings on this, thinking in general that the larger the diameter (to a point) the more realistic it would look. Both seem to have worked well for this image, I think. Soft shadow diameter was ~2.1m.
Let me know what you guys think, or if anyone else has more knowledge about these settings that would be willing to share that would be great!