It is better to use the standard library std if possible because it minimizes the number of external dependencies. For instance, since the introduction of C++11, a lot of Boost functionality is now available from the standard library std.

Sometimes there is a one to one relation between std and Boost such as boost::bind that is replaced by std::bind. But sometimes this relation is less trivial, e.g. to make a class non-copyable one should derive from the boost::noncopyable class in the Boost case:

class X : private boost::noncopyable {};

whereas in C++11 this is done differently by using "delete" for the constructor and copy constructor:

class X {
  X(const X&) = delete;
  X& operator=(const X&) = delete;
};