Unlike Chrome's bookmark sync, Firefox Sync encrypts your data client-side for privacy and security
Chrome 10 can encrypt everything client-side too.
Everything that gets synced -- bookmarks, preferences, etc. -- or just passwords? Do you have a source for that? I can only find evidence that passwords are encrypted client-side.
Hmm, good point. According to their documentation, "synced data is encrypted when it travels between your computer and Google’s servers" (this seems to refer to encryption in transit, i.e. SSL) and "As an added layer of protection, your saved passwords are encrypted on your computer and on Google’s servers using a cryptographic key."
http://www.google.com/support/chrome/bin/answer.py?hl=en&...
That does seem to imply that only passwords are encrypted while in storage. That's not surprising, since Chrome has a "master password" for password encryption, but unlike Firefox it does not require transferring an encryption key for your other sync data. (The client-side encryption key is the reason you need to "pair" your devices to set up Firefox Sync, instead of just entering a username and password.)
You're right, only passwords are encrypted, as evidenced in Google Dashboard.
You can also see your Chrome bookmarks in your Google Docs interface - so not everything gets encrypted.
2. Firefox Sync, which syncs bookmarks, tabs, passwords, history, and formfill data to all your different computers -- and to Firefox for Android. Firefox Sync encrypts your data client-side for privacy and security, and you can run your own sync server if you want to. (There are multiple open-source server implementations.)
See also: http://www.mozilla.com/firefox/RC/features/