Firefox stores automatically a few (?) previous changes to the bookmarks, in addition of your own backups from the bookmarks. I had a problem when I tried to sync, I got blank bookmarks and thought the sync failed the update and cleaned up my bookmarks stored in their sync servers. The issue however solved by itself in a while, after my ISP problems were fixed... the sync just failed but the bookmarks remained good at the servers. I'm sorry but I don't have the links which were helpful for me to get my local bookmarks back. You can google them up quite easily.
I still use Firefox over any other browser, because of the plugins I use in Firefox. I tried Chrome few times, but never could live long without my favorite plugin, NoScript. I don't know if there is an equivalent?