I'm with Jeff here; it depends on the animal.
Natural is not necessarily better. If you go simple (which I interpret as utilitarian), you are still meeting all the needs. You just aren't doing it in an as aesthetically pleasing manner. On the other hand, for some animals, the fundamental requirements entail naturalistic items. In this case, utilitarian and naturalistic are the same thing. Either way, just go with what works best for you.
1.0 Pastel Ball Python, 1.9 Normal Ball Pythons, 0.1 African House Snake, 1.0 Savannah Monitor, 0.0.1 Argentinian Horned Frog