DS does not debayer on the fly. R3D files are imported to .gen files using the SDK, and then the .gen files are what are used within the DS timeline.
If DS is debayering on the fly, then it is at an extremely low quality, as the native DS hardware won't support a high quality RT debayer based on the SDK.
Also - SCRATCH renders at this point would probably be slightly higher quality then REDCINE renders. Although much of the underlying render code is similar, the build of SCRATCH that is currently available to users is a few months ahead of REDCINE 3.18.