I personally prefer the P4 renderer on Poser 5, just because, to me, is three times or more faster than the regular renderer in Poser 5. Like before, when i was using Firefly, I would start rendering something, then I would go to chill out and read a book in my bed and I would read a bunch of pages before trhe render was complete. Now with the P4 renderer, I just lay down in my bed, start looking at just one page, and then i have to go back to my computer because the render is ready. Quality differences? of course there are, to me the shadows are much sharper and notorious in FF, but it's THAT much of an improvement as to choose it over P4R... now, if I need to do renders with big imported BG images, then I use FF because that's pretty much my only option.