It depends on how many documents you need to migrate. Briefcases work well because they preserve things like Creation Date, but I've heard they can have issues when they are very large (I've never had a problem).

You could create a Workflow that uses the Replicate Entries activity to automate the process and include error handling/retry functionality.

Either way, just be careful about space on the drives because when a briefcase is imported it unpacks the images and xml data to a folder on the app server before processing it into the volumes.