- One-based indexing
setting aside whether zero- or one-based indexing is 'better'; R and MATLAB have one-based indexing, so the convention is likely familiar to many in the Julia target audience.
still, as the OP says, (relatively) painless interoperability with C and C++ is an advertised Julia feature, both of which use zero-based index (although Fortran is one-based), and that mis-match is a definite obstacle to interoperability.