It seems unreasonable to say, but
Mable seems to stale to me while Maple (almost the same sound for pete's sake!) is fresh and sweet! If anyone were considering
Mable, I would always beg that they consider Maple instead.
That being said, you didn't list Maple and I do love
Maybelle, and I think it's because the of the emphasis on the "belle", as you explained. But then again, I really like frilly and OTT girls names, so that may be why!