Not to start up a dead thread, but I've been wanting to build a bass. I think it would be worth my fancy to buy two bodies, say one alder and one basswood, then compare. Use the same neck, hardware, and strings. No paint on the bodies just straight AB to a daw with no eq, then mic it from an amp with everything at noon. I think this would be pretty cool to see
A very rigorous test was done to this effect going even further than your model and e enthalyl removed the body entirely. Very cool and very scientific experiments, and I encourage anyone who still believes "electric solid body tonewood" nonsense to watch this immediately.
However if you watch this and still wish to conduct your own experiments, the age of the strings and the distance from the string to the pickups are going to matter the most. Also the accuracy of the performance matters a lot too so much so that you'd be better off at setting up something robotic to pluck the string so you can be sure the pluck is rhe same every time