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

class Something
{
    int m_a = 0;
};

is equivalent to

class Something
{
    int m_a(0);
};

So, doing

class Something
{
    int m_a;// (0) is moved to the constructor
public:
    Something(): m_a(0){}
};

yields a uniform syntax for initialization that requires or does not require run-time input.

Personally I don't like the first form because it looks like an "declaration then assignment", which is complete misconception.