If you need cutting-edge or esoteric statistics, use R. If it exists, there is an R implementation, but the major Python packages really only cover the most popular techniques.
If neither of those apply, it's mostly a matter of taste which one you use, and they interact pretty well with each other anyway.
If most of your job is going to be implementing data analysis techniques that you or someone else has done earlier and putting things into production, then Python will quite possibly be more suitable.
Actually, it is. When someone has only 3 or 4 years to finish their thesis and learning how to program is secondary at best, and they have to do it in a math-heavy department or field, there is no time or use to learn Python.