I've tried Tridactyl, Vimium, Saka Keys, Vimium C, and Vim Vixen. Of these, I found Vimium C to work the best and have the least overhead. Tridactyl added a consistent overhead of around 100 milliseconds when loading page, while Vimium and Vimum C added only about 20 ms of overhead.

In terms of features, I think Tridactyl is the most feature complete, but I found Vimium C to be more enjoyable to use. For example, Vimium C seems to produce better hints (e.g. fewer cases of hints for something you can't click on), when compared to Tridactyl. I also prefer Vimium C's "Vomnibar" over the Tridactyl interface, especially with a bit of tweaking to the theme.