Why does rendering on a PC take 10 seconds compared to 0.25 seconds in-camera?

And the complexity of the demosaicing software. More sophisticated software can deliver a little more details at a cost in image processing speed. See for instance the various demosaicing algorithms used in raw therapee (download the manual and read the paragraph entitled "Demosaicing panel" page 40). In camera jpeg converters trend to lagg in detail extraction compared to a raw converter run on a computer. You can see this difference here : look at where the lines converge the most: they are more clearly separated with a raw converter.

--
Thierry - posted as regular forum member