I still use Chromium (and Iridium, a derivative that hopefully doesn't send info to Google), specifically on OpenBSD, for reasons summarized here (lower chance of privilege escalation, limiting bad behavior):
https://news.ycombinator.com/item?id=21566041(...and discussed further in the parents of the above link, like: https://news.ycombinator.com/item?id=21559122 or the full recent related discussion here: https://news.ycombinator.com/item?id=21557309 ).
Given which, I might switch to Firefox for some uses after the next OpenBSD release where it will have pledlge/unveil support (preventing it from accessing the computer beyond config-specified limits).
Edit: One thing I wish I knew about firefox is a way, without extensions/add-ons, to limit which sites can use javascript/images/etc., and/or to open multiple config tabs at once to quickly turn those on by exception for occasional specific sites, as I do with chrome. Exception lists, even better. This was discussed a little bit at those above links.