My review of the Vr12 compares them a bit - that was the second one I got. What it comes down to, at least for me, is the clit stimulator, which is the main difference. The Vr10 has a more rounded shape where it hits, and the vibrations spread out more over the entire clit. The Vr12 hits me differently, and it's more like having a flickering tongue with the antennae above - it's much more intense. I like them both, depending on the mood I'm in, so I'd say it depends on the kind of clitoral stimulation you like.
Feel free to message me if you have other questions about them