Folder Sync 2 lets you compare pairs of folders and display differences using color coding. After comparing, you can choose to automatically sync the folders or manually manipulate the files (copy, move, rename or delete) directly within the Folder Sync window.
You can use the app for backups and for merging and managing content on external USB hard drives, Network Attached Storage, camera memory cards or any other drives from your network which are available through Finder.