Maybe being heavy has its advantage.
In my experience larger persons have to learn everything the very same way as others.
If somebody suffers from overweight he or she even has more diffiuculties to learn and to advance.
Especially the ukemi we do is not easy to do then.
One isn't better than the other.
In my experiences there are no advantages if being overweight. It's the other way round.
Overweight hinders training the way we do aikido. And as I said above there are not much people in aikido here, which suffer from overweight. You see this very seldom.
And aikido is meant to educate a person, to develop body and mind, to form a personality. So suffering from overweight or not is not only a "practical" question.