In my environment, when the Pixel Samples value is 100, a threshold value of 0.001 in Poser12 is equivalent to about 0.5 in Poser13, and 0.002 is equivalent to about 0.7. However, that may depend on the Pixel Sample value and scene content.

For that scene I tried, with a threshold value of 0.002, P12 computes about 3000 samples before processing the next bucket. P13 computes all 10000 samples, so it takes a very long time.

* Confirmed by watching the rendering progress bar

I seeked for a threshold value that cuts off the computation at about 3000 samples on P13, and it is about 0.7.

The result is similar quality with slightly faster render times.

Also, "with a threshold value of 0.002, P12 computes up to about 3000 samples" for that scene, so if the Pixel Samples value is 50 or less, P13 renders faster even with a threshold value of 0.002.