I think Vimium C works better than Vimium. It's been so long since I switched that I can't remember exactly why, though.
I switched last week because its smooth scroll is smoother.
I also noticed that Vimium C is better at finding clickable elements for hints.
one thing I like in Vimium C over Vimium is reload frame. Vimium it would reload the window and I have an older web app that uses frames where reloading the window resets everything back to a particular state and I have to go and reopen the frames.