Wish I knew, in general I couldn't find detailed article about Virus. It has some cryptic features like FM, morphing between two waves and phase distortion (according to WIki?), a set of waveforms (but which ones?). When combined, they give some impressive possibilities that not any synth I own seems to have.I think the OP needs to clarify what exactly they are wanting to achieve by getting a straight emu compared to a similar sounding synth
I would like to try it out and see if these features are actually useful / important for particular sounds. There must be something that makes Virus outstanding, right?