Hmmm... the huge modulation matrix on the supernova have features you simply will not find on other synths, I'm mainly talking about the Sync Skew and
the Formant Width.
These two characteristics which can be different for each oscillator combined with one slave sync oscillator for each base oscillator + modulation of any oscillator characeristic by LFOs and Envelopes makes the SNII capable of doing allmost any kind of synth sound you could imagine.
Another specific SN idea is the Soften filter which is also modulative and can in extremis shape a square oscillator to a sine. This is also per-voice settings.
About filters BTW. The main difference between the Virus and Q synths and the SNII is the type of dual filter they have.
The Virus and Q have 2 totally independant multimode filters per voice while the supernova has 2 multimode filters a "width" setting, which is more similar to Formant filters, and can create some seriously whack effects.
My reasons for some time in the future to get a Micro are those filters, though i don't think they'll be of as much use for me personally as the formant type filters.
The effects though is where the SN really kick in. The Q is a petty weakling compared to the supernova when we talk about effects.
On each of the 8 parts, you can have a different Delay, Reverb, Distortion, Chorus/Flanger/Quad Chorus/ensemble, Pan/Temolo, EQ (!!!) and a Comb filter modulative by LFO1. (no, the Q is not the only synth out there with a comb filter, it's in the EQ section)
The supernova has the best imaginable vocoder on any synth out there to add an extra plus. A psycho 40 band crystal clear one!! That's what we're talking about.