If we've learnt anything at the numerous tests at Bass bashes is that even bass players/owners struggle to tell the differences. I think the closest we've come to any agreement is that Rosewood fretboards tend to be "warmer" than Maple boards.
Personally, I agree with @Doctor J, that looks make a difference. If I like the looks of a bass then this will influence whether I fall in love with the tones.
If all of this is only a placebo effect then great...if others don't agree, so what...