Depends. As you said, this little rose-bomb must have had sustained power, something more focused, to the point. A nuke goes of an bursts away everything, makes it crumble. This little rose, however, kept heating its environment until stone was turned to lava. Now, this is a dumb comparison, because a nuke would easily blow off as much of an area as this little rosa AND have the effect of deadly radiation. So even when I´m saying that yes, the little rose is in ways superior to a nuke, a nuke is still more destructive.
Where I´d see the advantage for the little rose is against an enemy that might regenerate. Basically, I´d use it against someone like Cell or Majin Buu. Goku´s genkidama basically was a sustained force, as opposed to the usual hit-and-explode-attacks like a kamehameha.