The answers to this question have no chance but to fall under the same category as "who is the greatest guitar player of all time?" It requires an answer based on one's opinion or preference. Even if the answer is based on "the opinion of many, or , experts", it still is open to not being shared by all.
If you ask the "Greatest Guitar player" question to blues enthusiasts you wouldn't hear the name Randy Rhoads and asked of hard rock or metal fans, mention of the name Robert Johnson would likely be followed by "Who is Robert Johnson?"
The best information coming out of the "old guitar" question is evidence that some old guitars were made well; their woods and glues don't disintegrate after 10 years and the sounds they produce today are, at least by the opinion of many, not so displeasing to the ear as to render them useless.
If there were a measurable science to provide an answer, the difference measured over a decade may be so minute that a slight variation in temperature or humidity from location to location would likely negate the results of the study.
If it plays well years from now history has provided that the design elements and wood characteristics that created the once-loved sound will not degrade much over time.