You should try them both FIRST and also make sure to know about synthesis before you get a VA! Or at least, plan a few weeks/months to discover how it works
It's not about which one sounds fatter, it's about what you need for your particuliar style of music. I actually own a JP8080 and I used to own a Virus and both have a really different character. If you have only 1 synth, then I would say go for the Virus for more poly and multimode. If you already have quite a few synths, then the jp might be able to fill that gap