Did some searching on this subject and didn't find much, but here's what I do know:

it helps dedicate system resources to the render engine rather than Poser itself.

Makes rendering large scenes easier

My questions are these:

Why isn't Poser set up to do this to begin with?  It's like the difference between playing a game with software excelleration and hardware excelleration.

Why doen't it render in multiple threads even when I have 4 selected?

And is there anything else I could benifit from it?

first - it's not the default because it can have problems on some systems, also firewalls etc need to be configured to allow FFRENDER.EXE to pass through it as it sort of uses TCP/IP to talk to the main Poser program.

Poser uses buckets to render, one per processor (or core) in theory.  I have mine set to 4 and when I do a render, it starts in each quarter of the image.  The separate process version doesn't show it the same way (from memory - I don't tend to use it myself, I only do test renders in Poser before exporting to Vue for final renders)

One benefit you get from it (if you have enough RAM) is that Windows allocates memory to FFRENDER separately from Poser which means you are less likely to get out of memory errors with big scenes

ahh, a simple answer that made sense, thanks for the tips :D