I think it is just personal preference. It is my understanding that CM used nature study for science for the younger grades, which works great, but for some they want to branch out, and I say go for it 🙂
We have used all the Apologia Exploring Creation elementary series of books for 1st-6th grade and really enjoy them. We enjoy nature study and learn a lot there, but I wanted something different and Apologia worked for us. The lessons are still short and we add in oral narration and making journals about what we learn. There are other optioms, I only mention Apologia because it is what I have used.
If there is a subject that interests you and your students right now, go for it. 🙂
CM was an educator with fantastic methods, but I do wonder what she would do in this day of age with the variety of books and availability of options. Not that the methods would change but the variety might change because of more options 🙂