So are you looking at the speed that a certain set of values performs or are you wanting a better end result picture?  If you want the same image quality then P13 can use lower values.  Kind of like I can paint a board in 2 coats but I was told to use 10 coats, the extra time does not result in a better covering just more time spent.

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13