I believe the Java is brighter due more to the fact that it has substantially more baffle than the V16, rather than chamber size (by the Theo Wanne definition, the Java and Jumbo Java have "medium" chambers). It's not a super-high step like on the Jumbo, but it's still rather large. Different reed choices always confound these kind of things, though...
If your music store doesn't have a Java in stock, might you consider taking one on trial from WWBW or another retailer like that? You can always return it if you like the V16 better. In fact, why not take a trial period on both? I don't know if your music store does mouthpiece trials, but if they don't, this route would probably be much easier to try both.