There are plenty of paid-for utilities on Apple Mac OSX which compare files and folders.
What many people do not know is that Apple give you an excellent tool for free, part of Dev Tools.
Install Dev Tools, or download it, and look for /Developer/Applications/Utilities File Merge.
Not only can you put files into the two windows, you can put in folders as well.
Click 'compare', a new window opens and after a few minutes you'll get a listing.
Items in grey means that folder/file is identical, items in black means there is a difference.
To see how the files/folders differ click an item and you get message at the bottom of the window.
- “added to right” - the file/folder is only in the folder on the right
- "added to left" - the file/folder is only in the folder on the left
To make it easier to see what is different you can use the Exclude boxes in the upper right.