claudine wrote:
It seems to be a question of quality vs quantity?
Also a question of playing style, I think... on a 20-button you will probably be playing "along the rows" like some of the older trad players, such as Kitty Hayes (who plays tunes, naturally enough, in C rather than D, etc.), or "across the rows" like most of the modern players using 30-button C/G concertinas.
I'm not quite sure where Mary Mac Namara fits into this picture, but I seem to remember reading that she uses a predominantly "along the rows" style. Need to hear from somebody more knowledgeable here.
(Where are all those tina players who insisted so vociferously that this forum should cover concertinas as well as accordions, and have since contributed SFA to it?

)
But it's not as if whatever you learn on a 20-button will be useless if you move up to a 30-button, just that you may end up learning a rather different style of playing to get the most out of the 30-button instrument.
So sure, why not go for it?