My view is that it depends on how future proof you want your chuck to be. If you are happy with your current nova jaws and cant ever see yourself wanting anything more or different, then it really makes no difference whether you go for a nova or a vicmarc or a sorby or any of the others that take nova jaws. They all do the same job to more or less the same level. Its just the price that differs.
On the other hand, if you feel you might want to get other jaws in the future, then I'm with Doug. Get a Versachuck from Toolpost. They might not look quite as pretty as an Axi Evolution, but they are accurate, bomb proof, and will accept any jaws on the market from almost all the makers. I am so convinced by the concept, having owned and used one for about the last 8 years or more, that I really cannot understand why anyone would want to limit themselves to one make of jaws by buying anything else.