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
I've tried a bunch of these "vim-like" plugins and I always come back to Vimium (on Chrome). On Firefox I'm stuck with Vimperator, which means I don't use Firefox very often.
Why so? Firefox is still my browser du jour mainly because of Vimperator. I also use Vimium when in chrome, but Vimperator is way more powerful, and plugins are trivial to write: https://vimpr.github.io/plugins-en.html
I tried Pentadactyl and Vimperator before settling on qutebrowser. It's just fantastic and worth checking out if you're in the market for a keyboard-driven browser.
What got me to make the switch was that it wasn't Firefox. I got so fed up with Mozilla's bullshit that I went looking for anything else, especially after they broke all of my custom addons. Qutebrowser ended up pleasantly surprising me.
For another approach to power-tooling your browser, have a look at Gleebox (http://thegleebox.com/). I use it constantly to navigate between pages, to get a readable version of the page (!read), and to switch between tabs using a fuzzy-search approach. On some sites I've even added custom jquery-based selectors to quickly navigate around the pagfe.
Since Firefox now supports great parts of WebExtensions (https://blog.mozilla.org/addons/2016/08/12/webextensions-tak...), I am curious if this works natively in Firefox 48? (or Firefox Developer Edition, which is at 50 now and might have better support and more bugs fixed)
I think that's an assumed EOL on Pentadactyl because of Electrolysis. The devs don't talk but the community is trying to come up with a way to continue. Vimperator has similar issues with Eloctrolysis, I think?
I hope pentadactyl makes it, cos it's my favorite of the vim extensions. Vimperator just doesn't feel as advanced.