gerardi is ok, when grown in sunny las vegas, but may not bear same-quality berries in colder regions.
i have tasted issai and was not impressed. Black beauty is excellent, and to me is the best of all berries-- but only if you obtain a true Morus nigra. Many nurseries name their Morus alba’s “Ever-bearing Black Beauty”, or simply just “Black beauty”, and are mediocre to fairly ok(at best). Wet soil renders the berries(of fake black beauty) watery and bland.
gerardi and morus nigra are two of the slowest-growers have grown. Painstakingly slow where am at, so they could be considered ‘dwarfs’.
have seen multi-centenarian nigras posted by our european members, and they are rather large trees, so the dwarf label is only because they grow super slow.
photos abound on this page — Purple reign