I frankly don't think it makes a ha'porth of difference. I recall seeing Segovia at the Festival Hall many years ago - he was in his 90s then - and he had short, fat little fingers like sausages!

I have no problem with stretches. I have medium size hands and my little fingers just come up to the 2nd joint on the ring fingers. I think it's flexibility, co-ordination and strength that matter - and they all come from practice. :-)