If measurements show an audible difference, no one here will argue against the proposition that you can't actually tell what any given random person might prefer between two devices, even if one measures "objectively" better. Preference is, obviously, personal and subjective.
If measurements show no audible difference and someone claims a preference anyway, there's one of two things going on: Either we're measuring the wrong things, or that person is deceiving himself. Your ears aren't magic, and there's nothing you can hear that can't be measured - in fact, our measurement devices are often far more sensitive than your ears. Occasionally we do discover that we were measuring the wrong things and missing something - this is discovered by people doing blind tests and consistently showing they can tell the difference between two devices when they measure similarly. The overwhelming majority of the time though, if two devices measure similarly, you will be unable to tell the difference in a properly controlled test, and any perceived difference in an uncontrolled test is because levels are different, settings are different, or (as is the case with cables and 99% of audiophile "tweaks") the listener is just fooling himself.
If you actually look through the responses in this thread, people are genuinely interested in why the OP perceived a difference and are suggesting possibilities - the most obvious being that there's a setting on one DAC that is compressing dynamic range. No one is telling the OP he's crazy or stupid or just wrong.