The C tuning is standard on the plectrum banjo. It allows a rich variety of moveable chords, and has a close interval between the 3rd and 4th strings, to facilitate melody playing as the fretting hand moves up and down the neck. The lead banjoist in the Red Lion Jazz Band had a plectrum banjo tuned this way.
On the 5-string banjo the G tuning (G,D,G,B,D) predominates because it makes it easy to play in the key of G. The open strings are used a lot, and ring out agreeably. The keys of C, C minor, and G minor work well, too. And the reaches with the fretting left hand are comfortable.
The C tuning (G,C,G,B,D) is often better for the key of C. The open C string sounds a note belonging to the important C and F chords.
Furthermore, the lowest note in some tunes is the tonic. Play the tune in C with the C tuning, and that lowest note is the open C string. You can see how that works in the fragment of “When the Saints Go Marching In” above.
You can see the whole arrangement, and listen to it, in TEFView. Go to the following site, select “cb When the Saints Go Marching In,” download, and play it in TEFView. https://drive.google.com/drive/folders/19SdgeHixtx7XZz2TfHeVa5Yw4scPUOyS?usp=sharing