My thought is that a spruce topped koa bodied guitar is probably less likely to be a dud, percentage wise. But the big appeal for many is the stunning visual beauty of a koa top. And those can vary quite a bit tonally. Of the two hat I own, the GS with the spruce top is a little better, but costs considerably more than the GA size 424 LTD did, so I would expect more. Both are quite nice, but in a photo, the all-koa one wins.