Quality of render is a subjective thing. As an overall statement of the quality of a render produced with one over the other, I'm going to say that it doesn't make one whit of difference. As Noted earlier, it shouldn't. All renderers output the same quality of render, if you define this as overall appearance of an identical scene utilizing identical setups (redundancy intentional). Ultimately, they will both output to the same source -- the only differences are going to be improvements in antialiasing and such. The quality of a render is not the basis for judging it. It is the feature set of the rendering engine, and what those features make possible, that is the basis for judging a rendering engine. By that basis, the Firefly rendering engine exceeds the P4 engine. For speed, it is generally a truism that the more features you use from a render, the slower it will go. Doesn't always apply, but then, the one that it doesn't apply to typically cost more than Poser all by temselves, lol all of that said, I'll say that the use of the Firefly renderer requires you to learn a lot more about lighting, as it is much, much more sensitive to light and shadow and does a better job of handling them. Now if only they'll add in a point light...

thou and I, my friend, can, in the most flunkey world, make, each of us, one non-flunkey, one hero, if we like: that will be two heroes to begin with. (Carlyle)