Not a particularly scientific approach in my case, but I've been rendering a simple scene using a reflective sphere (reflection node), a skydome and a checkered textured ground. Lights were 1 IBL with image map attached and 1 infinite light (NB - shadow mapped shadows just don't work with reflections in P6, in P7 they did but took over an hour and a half for the scene to render!).

In P6 Firefly with no texture filtering and 1 raytrace bounce the scene rendered in about 5 minutes.
In P7 Firefly with no texture filtering (darn that default image node setting!) and 1 raytrace bounce it rendered in closer to 8 minutes (1 thread, seperate pass).

It could just be my machine, but I noticed that in P7the render got progressively slower in the bottom half of the image regardless of whether it was dealing with reflections or not. This wasn't the case with P6, where although it took longer to render the areas where reflections were happening as opposed to other areas, the relative speed looked about the same from top to bottom of the image.

Conclusions for me - my machine favours P6 over P7 for rendering relective/refractive surfaces.
Other scenes without reflective surfaces have rendered faster however.

My machine: AMD Athlon XP 2200+ 1.79GH, 1.00GB RAM, Nvidia Geforce 4 MX 440 with AGP8X, running Win XP Home.

 

PoserPro2014(Sr4), Win7 x64, display units set to inches.

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