So first a question, and then.... another question.

The first question is seeking some advice. Obviously this game is played in a virtual 3D world. The assets are 3D. The ships are 3D. My question is, would it be better, both in terms of rendering speed and data size, to create several versions of each sprite, to view the object from different angles, or to create full 3D models for the ships and the spherical map objects (the irregular objects will be rendered differently).

If the common consensus is the latter (3d models), is there someone here who has experience making them?

It sounds like the latter option might be better. The first option sounds like it would take up a lot of memory, depending on how big your sprites would be, and how many versions of the sprites you would need.

Unfortunately I have no experience in making 3d models, but hopefully someone else does!