I'm not a expert by any means and certainly not a teacher but if it was a choice between tone and playability I would take playability any day. A guitar that frustrates you every time you play it isn't going to be one you pick up very often. If you find things progressing well with the shorter scale you can always go back to your wife's guitar and see if things have gotten easier. Maybe trying different brands of strings will get you a better tone on the shorter scale.