C++ - initializing variables in header vs with constructor

Question

Regarding the following, are there any reasons to do one over the other or are they roughly equivalent?

class Something
{
    int m_a = 0;
};

v

Answer 1

The first form is new to C++11 and so at this point isn't terribly well supported, especially if you need to support a variety of older compilers.

Otherwise they should be roughly equivalent when a C++11 compiler is available.