the only jap jazzies' that are alder are the sunburst ones( i believe) all others are basswood.
to be completely honest, you will not notice a difference.
if you have two guitars identical in every way, cept one is bass and one is alder, you will only notice a slight weight difference(maybe 1.5 pounds at most)
as far as sound you will not notice much goin on.
alot of people don;t want to hear it, but truth be told, the type of wood you use for an electric solid body has little to nothing to do with the sound.
*edit* upon reading the descript, you know it has different pups in there, so it won't really sound like a jazzy normally does.
and i remember that the jag-stang is basswood, so is the 69 re-issue mustang, and a handfull of ibanez stuff is basswood. same thing with washburn.