I think the differences will be subtle, but sonically, I'd expect differences. Functionally one piece of wood in some ways, but not all. Sound does funny things based on the medium it's traversing, even more so depending on how multiple mediums interface. Subtle, but there. Can anyone other than EJ hear the difference? Beats me. But just as there are verifiable sonic differences between carbon comp resistors and metal film resistors in some parts of a tube amp circuit, I'll bet there are differences in the sonic results of how (and how well) a neck is attached.