I much prefer data and hard evidence too although I grudgingly admit psychology is a science too. Maybe not as accurate as other sciences so it's not as easy to measure. Still the human mind definitely plays a part in everything and it certainly affects what you hear. For that reason I don't completely discount things that might not be having a physical impact but just "all in my mind".
It's like the placebo effect.

In any case it still comes down to the player as far as the audience is concerned. I've seen guys playing mind-blowing stuff on cheap budget guitars. But give me a $5000 custom shop special and it will sound like crap.