Just on the whole "better to have loved than lost" thing...
My take is that the one who has had love knows that they are capable of being loved, and they can believe "if it has happened once, it can happen again." Even if they had the perfect relationship and then lost it and are sent into crushing despair or whatever, they still have this small hope.
The one who has never loved does not have this reassurance, and is left to believe that they are ugly/mean/completely useless. It causes them to get a distorted idea of their self-worth, which will affect them in more areas of their life than just romance.
I don't think that the matter of 'whether one knows how love really feels or not' enters into it as much as this does.