First, scrap your basic paradigm describing road and hybrid, because it's wrong and leading you to ask the wrong questions.

The reason hybrids may have more radically sloped top tubes than road bikes are diverse: road bikes have what is called 'compact geometry' for performance reasons, namely to make the frame less flexible and lighter by reducing tubing spans. Hybrids have sloping top tubes for two primary reasons, first to fit a wider variety of rider heights for a given frame size, and also to locate the handlebars higher for more upright, and ostensibly comfortable, rider position.

So sloping top tubes vary not only in degree, but intended benefit, so practically one is not better than the other (understanding road bikes do not, in general, have horizontal top tubes anymore).