I don't know much about AMF, but the little I have read and heard is that for the most part it is a good company to work for.
Same goes for AirNet. There is always "issues" and room for improvements. For a 135 operator that flies freight at night I don't think you will find much better.
In the end it all boils down to what you want out it! Without more information I can't add much to what already wrote.
GL,