The C printf family is still the gold standard of performance for formatted I/O, but woefully fragile and inextensible. C++'s iostreams offers important advantages in type safety, but struggles with performance and internationalization.

A number of projects, such as Boost.Format, try to the advantages of both. Here's further discussion about one such library we linked to recently:

Comparison of C++ Format and C library's printf

by Victor Zverovich

From the article:

I was recently asked on GitHub why would someone use fmt::printf, which is a part of the C++ Format library, over the standard C library printf. This is a fair question and so I decided to write this blog post comparing the two.

Disclaimer: I’m the author of C++ Format, so this is all very biased =).