The difference between [them] is if you have certain special characters in text fields; for example, an accented (foreign language) character. If you export as Windows CSV, those fields are encoded using the Windows-1252 code page. DOS encoding usually uses code page 437, which maps characters used in old pre-Windows PCs. If you export as one and then import with a tool that expects the other, most things will look fine but you'll get unexpected results if, for example, you know someone with an umlaut (or other foreign character) in their name.