It does not seem like a big deal, both conventions are easy to understand and natural to use. Except if you work with the discrete Fourier transform. Then 1-b

It does not seem like a big deal, both conventions are easy to understand and natural to use. Except if you work with the discrete Fourier transform. Then 1-based indexing is extremely cumbersome and annoying. More generally, if your indices are to be understood "modulo N", it makes sense that they are all strictly smaller than N (or even signed, and centered around 0).