What is better for importing, XLS or XML or XML from MSP?

Importing project data from MSP is definitely better than using an XLS file. Primavera, both the client and web support importing XML files. There are out of box import options for XML and XML MSP files, so that Primavera will look at the fields that are in MSP and migrate the data to the fields that are in P6. When doing these imports using XLS, you really have to get the naming conventions spot on, the fields have to be perfect, the data in the fields needs to be perfect. If you can get the XML out of MSP, most of the fields/attributes are already housed in P6 for the import. There is TONS of support in the user guide for working with XML files and working with MSP and XML files. The user guide lists the following for XML imports. docs.oracle.com