I have to respectfully disagree. The amount of "stiffness" between types of wood is so small as to be irrelevant. If the components are strong enough to counteract the pull of the strings, then the mass is stiff enough to not be affected very much by the vibration of the strings. People go on and on about the wood of the body, neck, fingerboard, etc. but ignore the potential differences in electromagnetic components, which would have a much greater effect:
- Pickup windings (how many does it take to change the sound? Can you show two pickups are wound exactly the same?)
- Pickup height
- Quality of the solder joints
- Pot quality/cleanliness
- Shielding
- Strings in general (that's a hole with no bottom!)
Does a body made out of concrete, aluminum or legos really sound that much different than ash or alder, etc.? Could you tell the difference in a blindfold test? After all, the "stiffness" of these materials would vary greatly from any kind of wood. If you play a bass unplugged, are any differences clear-cut? I would think if the wood really mattered, then playing unamped would reveal a great deal of variation, since you've removed the electromagnetic forces completely.
As I've stated before, the idea that the wood imparts some contribution to the sound is partially based on the fact that it does affect the vibration of the air within an acoustic instrument; that can't be denied. But an electric instrument only superficially resembles an acoustic one. All that matters is the string vibration in a magnetic field; the wood has little or no effect on that (certainly less than the things I've listed); it seems counter-intuitive to many people, just like the idea that the Earth moves around the Sun does not appear to match what we see. But what we experience does not always conform to reality. It's the aural version of an optical illusion. Thinking the wood affects the sound affects how the sound is perceived.
I realize many people disagree with this. Vehemently. But with people having their own opinion on which wood sounds "brighter" or "darker", it points to being very subjective, not objective.