Acrobat at least hasn't been relevant for over a decade outside of niche concerns (like javascript-enabled pdfs, which I have seen exactly twice in the wild... these should be illegal by the way). You can't say the same about microsoft.
This is not true IME, because PDF and PostScript are so tightly coupled. If your PDF renderer doesn't tightly align with Acrobat, it's highly likely to not print correctly, hence Acrobat __is__ the spec.
