Vimium mainly gives you keyboard navigation, but QuteBrowser removes the address, tab and bookmark bars and instead gives you keyboard access to everything via the very Vim-like status bar at the bottom. Incidentally this also frees up quite a bit of vertical screen real estate, which is a big deal to me. Browser settings, scripts, etc. are also all accessible via the keyboard — Vim style.
Edit: The lack of a solid Bitwarden integration in QuteBrowser is kind of hurting though.
I wouldn’t say they do the same thing exactly. Vimium is similar to a vim-mode in something like VS Code, while qutebrowser is more like Vim itself. The Vim “spirit” is built-in and is the expectation rather than a layer added on top. The qutebrowser UI, already minimalistic, is also very configurable and scriptable.
The flip side to me is that some of the experience will be nicer with Chrome, the same way VS Code can be nicer and easier to manage.
Assuming you're on Linux, that's usually more of a problem with Linux distributions being behind on QtWebEngine. Though yeah, sometimes things are tight with QtWebEngine only updating their Chromium baseline once every 6 months. I try to ship workarounds (in the form of polyfills) with qutebrowser when I know about breakage, but usually for me things run smoothly.
Unfortunately, support for proprietary codecs like MP4 and such requires building Qt from sources, and would also require me to acquire licenses for them all (I believe they're free until a certain number of distributions, but also with all the indirect ways you can get qutebrowser, I can hardly even provide that information).
This isn't an issue on Linux, because those licenses have some sort of exception in the sense of "if shipped with an operating system or its packages".
Homebrew seems to build its Qt packages against system ffmpeg with proprietary codecs enabled, and there's an issue open which would at least allow you to build a custom build against that: https://github.com/qutebrowser/qutebrowser/issues/4127
Maybe I should look into whether I'd be allowed to redistribute such builds (or what kind of paperwork I'd need to do for it). Unfortunately there's a lot on my plate, and macOS/Windows are admittedly somewhat second-class citizens as I don't use those myself.