YouTuber studentsmusic did an extremely detailed comparison between the iVCS3 and its vastly more expensive hardware counterpart. He's done a fair job of editing down a whole hour of tests to just 20 minutes.
Some additional Infos: excerpts from trying to get objective data comparing an app with the original synthesizer. Don´t take it for granted, especially comparing waveforms here in such a short feature. So probably with mistakes, but somehow the tendency: the app is quite good! One core challenge that should be done better is comparing the filters, which might behave different in every hardware device and are one important character of the ems synths.
Interesting: Sine (sorry for german/latin "sinus") wave on AKS AND IVCS is not pure and has quite some harmonic distortion (due to Wave shaper?). Normally around 5%THD. The sine of the self oscillating Filter should be around 3% THD. Here its more, but somehow congruent analog and digital!
Of course there can be endless discussions comparing virtual with analog vintage. We all know its two different Animals. But as it comes to sound and hearing this might be a trigger for you to check by yourself, whats cooking with your hardware/app gear. Believing is not knowing.