I use Firefox as my primary browser on desktop, it's pretty much the best combination of performance, UX, and plugin ecosystem. Chrome was good for a cool decade but I just didn't like the fact that it was built by an ads company.
Arc attempts to create new concepts in browsing, like a sidebar that's not just a collection of tabs but almost a reflection of how web browsing is thought of within your mind, e.g. tabs for work are separate from personal browsing, and maybe a specific tab doesn't need to stick around for long so it just disappears. The whole experience does feel a bit sane compared to using Chrome or Firefox.
Then there's Kagi's Orion which attempts to make the browsing experience less annoying by removing all the trackers and ads without any 3rd party plugins. This is super nice, especially on mobile where even my Safari set up with 3rd different extensions attempting to block ads just fail, Orion seems to just block those ads.
Below is a comparison of browsing the same site on mobile using Safari and Orion.
I'm going to give Orion a solid week of trial before making a full switch but I am pretty happy with it on mobile. On desktop, it's going to be my "focus" browser where I don't need distractions, especially while writing and Orion's focus mode is perfect for this. Arc has this too but that might not be enough for me to switch over.