David--I have no interest in tethering--just looking for the best image quality possible. Canon's point is that their software is directly engineered for their cameras. They don't provide information to 3rd party developers, so Capture One and others need to reverse engineer the software.
Hi,
While there are (probably) some unused proprietary features in the Canon Raws, the main task of a Raw converter is to achieve a high-quality Demosaicing of the Raw data. In my experience, Capture One and RawTherapee provide the best conversions on both Mac OS, and MS Windows OS. Capture One currently even achieve a higher resolution conversion, with fewer artifacts than most other converters.
After the demosaicing step, there are many possible ways of processing the still in linear gamma Raw demosaiced data. Good profiles and good resampling are often the basic factors for success, the rest of the tools help with an efficient workflow.
Cheers,
Bart