I bought the Rubin for my daughter who has been learning on a rented accordion for the previous six months. It was recommended to me on Reddit for the following features:
* Light weight, so suitable for a child of seven
* Slightly narrower keys, which means they're easier to reach plus there are four extra treble notes as compared to normal
* Welmeister is a quality German manufacturer, so it should sound good
* Choice of two treble voices
* She liked the look of the blue on the Thomann website!
Unfortunately the first one arrived damaged, but Thomann aranged for a return, and the second one arrived safe and well.
What can I say, but she and I are both really happy with the purchase. Compared to the rental accordion I'd say the sound has the following improvements:
* The bass is a lot stronger
* Both bass and treble sound "richer" somehow. I don't know how to describe it better than that, but it's the word my wife and I chose.
* The Musette voice is a lovely traditional sound.
I'm really glad I decided on this model.