I loaded your image into Photoshop and tried adjusting brightness and
contrast to better match the two halves, as brightness and contrast
appeared to be the major difference, with a smaller sharpness
difference.

The silkypix image is slightly sharper, and the blown highlight on the
little knobby thing is smaller with Silkypix than with Capture One; but
these differences could easily be explained by settings within each
converter - how much usm or sharpening applied, if any; whether the
exposure control was higher on one than the other, producing a bit more
blown white, whether  contrast adjustment was used, etc.

I think the differences are not enough to pronounce judgment on which
converter is better, unless we know in detail how each was set up.  Even
if each was run at its default settings, there is no guarantee that the
defaults are equivalent.

Personally, I use DxO Optics Pro, which I find is excellent, though
expensive.  You can download a trial version if you want to try that
against your current ones.

Colin D.