The Dixie II+ is a basic VCO. It really doesn't do much more than any other basic oscillator. It has a sub oscillator, which is a nice feature if you make a lot of bass sounds or a sub factors into the sound of your patch (not always bass).

The Rubicon 2 is more of a complex oscillator due to its "through zero" capabilities among other features. You'll also see that reflected in the price. You can substitute the Rubicon for a Dixie... but not the other way around if you start diving deep into features.

I have the Rubicon 2 and I'm considering the Dixie as an additional VCO... I have a Z3000 but prefer the workflow of the Intellijel stuff.