Surfingkeys has a couple of features over cVim that I really like:
-pressing '?' on any page will open the list of shortcuts
-searching through bookmarks / history ('t') is prettier
-very useful feature of switching through all the current open tabs with link hints ('T')
There's one shortcoming I noticed, however, is that when you go to the link hint mode, there are no indication than you entered it. On cVim there's a "follow link" notice in the lower right corner.
I'm a fairly casual user though, someone else will probably find more differences and pros / cons for each extension
Now how do they compare?