Streams are the canonical way. Try making this code work with printf:
template <typename T> void output(const T& pX) { std::cout << pX << std::endl; } Good luck.
What I mean is, you can make operators to allow your types to be outputted to ostream's, and without hassle use it just like any other type. printf doesn't fit the the generality of C++, or more specifically templates.
There's more than usability. There's also consistency. In all my projects, I have cout (and cerr and clog) tee'd to also output to a file. If you use printf, you skip all of that. Additionally, consistency itself is a good thing; mixing cout and printf, while perfectly valid, is ugly.
If you have an object, and you want to make it output-able, the cleanest way to do this is overload operator<< for that class. How are you going to use printf then? You're going to end up with code jumbled with cout's and printf's.
If you really want formatting, use Boost.Format while maintaining the stream interface. Consistency and formatting.