Hi,
the two functions are very similar, but get_cfg_var() is the older version and will work with the most php versions. The disadvantage of this funtion is, that it reads the Master Value and not the Local Value. Check your phpinfo(), you will see that the configuration part has this two values. In most cases, the Local and Master Values are the same, but not in your case. For you, the Local Value for safe mode is set to off, the Master Value to on. The function ini_get() reads the Local Value.
I think i will change this for future versions.
Greets Jan