

The 6000 series is faster in Raster but slower in Ray Tracing.
Reviews have been primarily pushing cards based on RT since it has become available. nVidia has a much larger marketing budget than AMD, and ever since they have been able to leverage the fact they have the fastest Ray Tracing, AMD share has been noise diving.



https://www.reprap.org/wiki/RepRap
The work has all been done long time ago.
The designs and software are all open source at this point.