The CS-80 is one of my fav virtual synths. Never used the original, so I can't compare, but anyway it's a truly inspiring machine. And I think that's the most important thing when it comes to musical instruments. It lets you do so different things, very flexible.
The Mini is another powerful instrument, which adds several features to the original, so comparing them it's just a part of the question. If you need good basses, leads you know you can trust it, but you can do more with it, being polyphonic. There's "meat" in these instruments, and that's a good sensation to me!
The ARP, well, I just spent a little time on it (and it deserves time!). But the first impressions have been great. When I started using it I had, probably for the first time, the impression that 70's are back! Those nuances, those drones... well to me it's wonderful to have these sounds coming out of my computer... it's just pleasure!
I'm not an engineer, and I'm not a vintage circuits expert, sorry. I'm more a music lover
Last things: all these softwares are really enjoyable when used with real knobs, not with the mouse! Hearing the presets is good, but when you start tweaking real knobs with your fingers it's another story! Get a good controller!
Hope I've been helpful. Anyway we're talking about very different instruments, so it depends on your specific needs.. but if you have money.... well...
