Can't speak to the ease of texturing Poser figures in Bryce vs Carrara. I used Bryce a lot but not for Poser. Rendering is much faster in Carrara. I don't know the technical specs for the Bryce render engine but I don't think it has many of the optimizations that the CS3 engine has for speed plus the Global Illumination render engine is very, very cool.

Bryce beats Carrara for skies and terrain modeling. With CS3 Carrara has comparable texturing for terrains and has always had better texturing for non-terrains.

For complex scenes such as Poser figure rendering, I much, much prefer Carrara's lighting, texturing and rendering.

I used Bryce for 4 years before finally tiring of its limitations. I switched to CS3 this summer and have never looked back.
One other point: since I switched this year, Eovia has put out a very powerful enhancement (CS3) whereas I hear Bryce may be end-of-life.

Marc