I think C2 is better. It surpassed raytracing in this version. Global Illumination and Indirect Light are 'real world' light circumstances that a ray tracing engine can not produce easily. In Carrara 3 this gets even better with softedged raytraced shadows, but the features I read on the curious labs site, regarding the FireFly render engine were already in Carrara 1 (even in Ray Dream, as I remember correctly). Still, you can make great renders in Poser5, but mostly if you want typical 'studio' portraits and stuff like that. Upgrading is a good idea, for 'extreme ultra mega photorealistic images' if one wants to do better than the C2 marketing-talk (are you sure it is not referring to C3?)