I'd distinguish between differences that anyone can detect but some may not care about, and differences that may not be objectively detectable at all. Muscle cars, at least, are different in a way that anyone can see. Push that pedal to the floor and it feels different from a Honda Civic or whatever. Whether that difference is actually interesting or good is, of course, a matter of taste. Whereas audiophile nonsense is often indistinguishable even to the connoisseur and depends entirely on some form of self-deception. Still could be worth it, depending on what one considers worthy.