Charles,
The back is just a very nice piece of mahogony, nothing more exotic.
There is definitely a difference between this one and the Wenge top 5str. It's hard to tell exactly what parts of the difference are caused by which differences. Besides the difference in top, the electronics are different and I'm using different strings. I have Alembic strings on this one (changed after the photos were taken) and Fodera Diamonds on the 5str.
As a brief/vague/bad description of the difference, I would say this one is more round and the 5str is more snappy.
I've also found that I favor the neck pickup on this one as it seems a bit mushy with both pickups blended equally.
However, with the 5str, I favor and equal blend of both pickups for more punch.
I'm looking into upgrading the electronics on this one to match the 5str. We'll see how that changes the character of the sound.
Sorry for all the quoted cliches! But it's REALLY hard to use words to describe subtle differences in sound. The degree of subtlety is such that I'm the only one who can tell the two instruments apart. Everybody else says they both sound exactly the same - both truly amazing, but the same!
Loch