Look, I believe in science and all but when you record and mix records day in and day out, the science has little to do with how your opinions get formed about the gear you use. For instance, if you've been making records for years at 44.1 with the same converters and then switch to 96, the difference may well be staggering to you. If it makes you produce better recordings and influences your mix in a positive way, it IS better. If you know your monitoring chain intimately along with the rest of your gear, it might be easy to perceive the benefits/shortcomings of the switch just based on how it influences your decisions. You may find, for instance, that reverb tails sound clearer and transients have more detail and that makes you work differently and have to work a little less harder to get where you want to go.
I dunno, we're a cynical bunch and some of us, like Ethan, rely solely on scientific proof to make up our minds about audio but when you're actually out there making records for a living and get more and more acquainted with your gear day in and day out, you will probably have a different perspective.
I say "cynical" because some of us don't believe anyone is qualified to make a decision based on listening alone because audio engineering is now such a convoluted, devalued art where EVERYONE is an engineer, it seems. Some of us think that when someone hears a difference, it's all in the mind. Audio is somehow now perceived as a working science - which it is to a certain extent, mostly to those who THEORIZE about it more than actually PRACTICE it - but it has never been that way for working engineers who make all the wonderful records that we enjoy. They simply knew how to masterfully execute the fundamentals. Technology is a tool and quite incidental to the program material. Sure, there's lots to know in order to make a good recording, but to me, trial and error and the process of deduction is a worthwhile way to form opinions.
If the guy says he hears a difference, great. Now use that positive influence to make better recordings.
Cheers
