I''m an MFC user too, and I know the Win32 API too. The MFC is good, because your work is dramatically reduced. There is no disadvantages for the Win32 users, but the Win32 code is usable anywhere in the MFC program. The MFC program''s developing time is very short, but the all possibilities are provide the Win32 API. Maybe the best solution is the mixed code.
The filesizes is really variable. Maybe someone was forgets set the compiler to Release version. My 1.5MB !! sized debug version is 60KB in release version.