My original postgraduate training was as a wood scientist and I have also built and repaired instruments. I don't think there is a "best" wood for instruments...it very much depends on the combination of the particular woods used, the structure, density and orientation of cut of the particular piece of wood, the design and quality of build of the particular instrument, your taste in aesthetics, and the sound you want and your style of playing.
My two current favourite instruments couldn't be more different: one is a highly abalone inlaid mandolin of BRW with an Englemann spruce top and ebony fingerboard and bridge...it has a bright, resonant and very penetrating sound; the other is an extremely plain octave mandola of honduras mahogany with a sitka spruce top and IRW fingerboard and bridge...this has a deep, warm and mellow sound. Both instruments perform their jobs excellently.
I have used IRW, BRW, koa, maple and mahogany with sitka, Englemann and adirondack spruce, Swiss pine, cedar and Douglas fir soundboards, and ebony and IRW fingerboards and bridges in many different combinations. Each has its own individual sound and at the end of the day I believ it's down to individual preferences.
I wouldn't use BRW or any rare or endangered wood now. Like 'Spaw I prefer "pear" hide glue as it works with a vey thin layer, sands beautifully and is easier to separate for repairs than modern synthetics.
End of my pennyworth!
All the best,