I work on a well-established, embedded C++ code base. We have been using a proprietary API to our filesystem. For better integration with third-party C libraries, we are currently in the process of implementing most of stdio.h and fcntl.h. I made what I thought was a non-controversial proposal that we should also implement the fstream class and encourage new C++ code to use it instead of the new (to our code base) C-style API. We already have the stdout parts of iostream available, although it is not widely used.

Given a choice between using stdio and fstream, what are good reasons to choose stdio for embedded software development in C++?