The very metrics we choose to base our 'facts' on are based on preference. I think if we were to lay out metrics we agree on, no one could argue about the measurements. But I somehow think the vinyl v. digital arguers are indeed not talking about the same metrics.
But at it's essence, it is not about measurements. They are merely tools to get us to some end---in this case, sense pleasure in the form of sound (and perhaps sense pleasure in the form of thought as well).
I think when people talk about the superiority of vinyl, they can only be expressing an opinion, it happens to be an opinion that does not regard some of the common measurements.
When people talk about he superiority of digital, they too can only be expressing an opinion, it happens to be an opinion that does regard many of the commonly chosen measurements.
In the abstract, the fact is, it cannot be a fact that digital is superior, it is simply another opinion.