Maybe, Carrara renders do have the edge on Firefly ones.   I think Poser is better for materials, though (and Carrara can't handle Poser materials).   Also, I reckon Carrara is actually worse than Poser at memory management.   I recently tried to do a scene with three figures in, plus assorted clothes, hair and props.   Carrara basically started to crash, once the third figure was added.   It struggled to save the file and then couldn't re-open the saved file (ran out of memory).   I did the same thing in Poser.   It wasn't completely trouble-free in Poser, either, but it rendered with the Firefly settings that I wanted.   My machine has 2Gb of memory, but I think Carrara hits a brick wall at 1.5 and it can get up to 1.5 in no time flat.

Carrara 5 lacks a lot of the Poser-equivalent features that Carrara 6 has, so 6 is  the only one (I think) that can be considered any kind of alternative to Poser.    Transposer's great, if you enjoy head-butting your monitor with frustration.