The only software synths I've ever used was the Bristol collection for Linux (et al), and for that mostly played around with the ARP2600. There's probably 30ish different models rolled in. It's free, but you're stuck with using Linux (et al), which is generally a miserable experience.
I also bought a VCS3 sim for my ipad which is fun but completely baffling.
I also bought a VCS3 sim for my ipad which is fun but completely baffling.