I had a chance to put my hands on a solid aluminium bass with a maple neck. The sound was amazing and that sample sounded as organic as you wish. It had an active pre which could go other ways, but it covered the JB ground irreprehensibly.
The weight was not different from a regular bass, the aluminium body has cavities.
They make excellent guitars too. I tried a model with P90 which has a very peculiar construction: it is made by a layer of wood, a single piece, body and neck. Over this is a layer of aluminium, again a single piece, neck and body.
Above all this the keyboard. It sounded very responsive and the P90s spanned from Telecaster to hollow body jazz territory.
For those interested, this is the guitar I mean http://www.alusonic.com/riviera.html.
Regarding the strings, it is quite difficult to tell the difference between the two models, they sound pretty much the same. If I had to express a preference, it would be for the low riders.