The spell-casting Druids have access to more spells. And to increase flavour and customisation in this sub-class, the 5E designers gave these Druids permanent access to a list of spells that are influenced by and evocative of the type of terrain in which they trained, or are working/living. That's probably why they went for Circle of the Land. It sounds pretty straightforward to me.
The shape-shifting Druids have access to more/better animal forms and can transform more easily. The animals they turn into can (eventually) be flying or aquatic creatures, so they are free to roam in the air, rivers or seas, not just on land. I don't know if the 5E designers wanted to allow a similarity between Druid shape-shifting and lycanthropy, which is moon-connected. The PHB explains that these Druids tend to gather at full moon, and some night hunter animals may hunt better with the moon. The PHB also handwaves that these Druids might be asocial and more wild and temperamental than your everyday Land Druid, and their mood is "changeable as the moon".
I guess the 5E designers could have called the order of shape-shifters the Circle of the Beasts. But I wouldn't have used Land for them. Yes, there is the spell Moon Beam, but they all have it so ... I'd say the shape-shifters might have been better named, but the spell-casters are perfectly fine.
Last edited by Drath Malorn; 20/04/21 02:02 PM.