I use FF and Chrome, but the sites I visit are distinctly split between these two browsers (i.e. I strictly browse some sites on one of these two browser).

First, I want FF to be around for a long time to make sure there's no browser monopoly by Chrome. That's the primary reason I use FF.

I also trust FF more regarding privacy. So I use FF to log in on sites like my banks, credit cards, and government sites (like IRS and social security). I even use FF to check my Gmail. I use Chrome to browse less trustworthy sites across the internet, and sites that I really don't mind Google tracking my visit such as HN, Reddit, etc. The only Google product that I use on Chrome is YouTube. :)

Thank you, FF engineering team for keeping alternative alive on the web.