Import threads and posts from PHPBB in two steps
 

I was wandering what is the best strategy to import and add threads and posts from a existing PHPBB Board to a VBulletin Board. Is it better to import PHPBB posts to a test VBulletin board and in a second step to import posts from the VBulletin test board to the existing VBulletin board or is it better to import directly posts from the PHPBB board to the existing VBulletin board.
Thanks in advance