I listened to both iSINE10 and 20 side by side for a long time with my DAP (3.5mm cable), and ended up buying the iSINE20.
Both iSINE10 and 20 does deliver the Audeze planar sound despite the small form factor. What I mean by that is the imaging is very stable from high to low, nothing jumping out at you artificially.
It sounds very pure and revealing because it has no artificial treble boost (e.g. metallic tube) or bass boost (e.g. reflex chamber housing) that a lot of other IEM makers add on to spruce up the sound. Some people might find it too "simple" compared to the more flamboyant earphones with body shaking bass or rich thick overtones.
The most surprising thing was that it made some recordings sound badder than I remember them to be, while some recordings sound better than ever. I think it reveals a lot more about the recording quality, like the sound stage and phase coherence.
I preferred the iSINE20 because the extra treble did give it a signature Audeze sound, and a more sense of space. I also felt more potential for iSINE20 to sound even better with the right amp, cable, burn-in, whatever. It had a bit of a treble ring initially (on classical piano solo etc) but it disappeared after running it in overnight.
iSINE10 sounds more coherent, and the image is focused centrally (not as splashy) meaning it is nicer for listening to vocals and guitar solos etc. It comes down to personal preference. My trusted friend insisted that iSINE10 sounds better than 20, but I bought the 20. In the end, I didn't buy the iSINE10 because it was the similar kind of goodness that my other IEMs can deliver (like T8iE, IE80, etc) while the iSINE20 was something else out of the ordinary.