My personal opinion (not pronouncement) is that the Old Bull is a hatchet job. I hold the same opinion about the Leduc scroll. In terms of conception and execution there is, in my opinion, no comparison between these and the Cannone, for instance, which is also a late instrument (but by del Gesu himself).
I listened to the itunes Ole Bull sound clips. My impression was - hollow sound of a regraduated (too thin) violin.
So I went to listen to excerpts from "Homage".
King Joseph - sounds right, not regraduated.
Lord Wilton - regraduated.
Are my guesses right?