In the admin console version of Shuttle, it can take up to 10 minutes to load accounts and folders that the migration job is planning to migrate into. This can lead to significant time to create a job and is quite manual.
In the standalone version of Box Shuttle, you could upload a spreadsheet that includes the source location and where it would be migrated into Box. This bypassed the selection of users and folders that can take a long time for our largest customers.