vCard is, I think, something Microsoft Outlook uses to save contact information in its address book. I don't use outlook, so I ignore that.

XML and CSV are two types of file formats. I think most people will find CSV easier to use (stands for "comma separated values"). A CSV file can be easily read by a program like Microsoft Excel or any spreadsheet program so you can view, sort and better manipulate your PMs.

The biggest drawback to vBulletin (the forum software) is that its PM system is a few years behind what an ordinary person might expect from an email system. I hope they continue to improve it in future versions.....