r11 has a significantly faster render engine than r10. It is faster than Carrara for GI but only if you intelligently use it's render settings. Of course it's also set up to use Renderman etc., so it's own render time isn't necessarily a good benchmark compared to Carrara since many times the rendering is farmed. Additionally, the GI and caustic capabilities are only available if you get the full Studio version or add the Advanced Render module to the base edition. 

C4D is kinder to the computer system resources than Carrara is - most of the time. But, you can bog your system down if you try. You can never have too much RAM.

C4D uses the "buckets" rendering scheme that high end software is migrating to. But to get the super realistic renderings, you also need to have the Advanced Render module. The lower end C4D doesn't come with it. 

C4D is in a different league so a straight across comparison, while the names of areas may be the same, the software render core, materials and modeling functions are not. And you pay for the league it's in. Plug-ins for C4D cost as much or more than Carrara Pro. I mean, hey, with Vue7  xStream, Vue functions as a real-time C4D plug-in.

Straight out of the box C7Pro will give you more functionality and capability than C4D standard.