So in either case, it's faster than P11? I felt like area lights were pretty slow to render in P11, so I wasn't sure.

The hard part with an area light is that the amount of blur depends on the distance from the light to the object, so it harder to get a sense of how much blur you will end up with. But you can adjust it by adjusting the size of the area light. The bigger the light, the bigger and fuzzier that blur will be.

I would think Poser could implement shadow blur by treating a point light as a sphere instead of as a point. That makes more physical sense than treating it as a trait of the shadow itself. I don't know how it was done previously.