Using FDupes

# run this command to install the fdupes command line tools for OSX Mavericks
brew install fdupes

# example of 2 directories
fdupes /dir1 /dir2

# real example of 2 directories
fdupes /Users/ryan/Dropbox/Camera\ Uploads /Users/ryan/Desktop/Phone\ Photos

# add the -d flag to prompt for deletion, in the form of 1, 2, etc. and 'all'

# Example of 1 directory
fdupes /Users/ryan/Dropbox/Library/documents