I'm a US-based broadcast engineer who hasn't worked on analog systems in long time, so I haven't had any direct experience with SCART connections. That said, there shouldn't be any difference in quality between S-Video out via a DIN connector or SCART on the same device. There's no difference in shielding, balancing, or signal between the two connectors. This forum post seems to agree. (Though it does sound like the device in that post has a termination issue, which might be something to check your VCR setup for.)
As best as I can tell, SCART never carries a digital signal. Some primarily professional devices (as noted in the comments to the other question), had RGB and color difference (YPbPr) component outputs which might have better quality and might not be available on a separate connector.