Does it prioritize privacy? I haven't used Firefox in a long time, so my impressions of it are based on news stories, like them launching a partnership with sketchy VPN services or building in "easter egg" advertisements for television shows.
I'm curious what you're using currently if Firefox's privacy imperfections are of concern? Safari?
(Firefox has a good security team, but Chrome's is unmatched.)
Secondly, that's a single step in the threat model; it's not just about what a Google engineer would do with your data, it's about attack surface area when any Googlers (or Google infra, or Google partner infra) that is compromised automatically exposes you.
The simple act of transmitting and storing your data to anyone, no matter how secure their systems are, is still by definition less secure than simply not transmitting that data.
In terms of technical implementations, Chrome naturally surpasses everything else in a naïve myopic comparison (and always will), but holistically a secure algorithm isn't going to protect you if you've voluntarily handed the keys to the kingdom to umpteen untrusted parties. Chrome gets all the technical details right in a context where doing so seems redundant.
They will also block all third party cookies effectively blocking most ads. Chrome or Chromium would never build in such a feature and make it ON by default. Because tracking and personalized ads are there business model.
Lately it introduced the ability to do "Multi-Account Containers". They behave like light profiles. But you can use containers to box social networks. See:
1. https://addons.mozilla.org/en-US/firefox/addon/multi-account...
2. https://addons.mozilla.org/en-US/firefox/addon/facebook-cont...
3. https://addons.mozilla.org/en-US/firefox/addon/google-contai...
This ability is currently unmatched in other browsers.
It also has built-in tracker blocking. Nothing you can't get with uBlock Origin or Privacy Badger, but it's nice to have it on by default, especially in Private Mode.
Note that people complain about the "strict mode" of that tracker blocking not being enabled by default. However I can tell from my experience that the strict mode breaks websites.
See also the design of Firefox Sync, which was designed to not leak data by default, as compared with Chrome's Sync: https://hacks.mozilla.org/2018/11/firefox-sync-privacy/
It's valid criticism but seeing this presented in arguments about why Firefox is bad (and you should be using Chrome instead) is absurd.
Firefox is significantly more trustworthy than Chrome (the outrage over Mozilla's occasional screw-ups exists because that behaviour is decidedly not the established norm for Mozilla whereas the same behaviour from Google surprises no-one).
The context in this thread was "Switch to Firefox. It prioritizes privacy, unlike Chrome". In other words, "Firefox is more privacy-focused than Chrome".
Piling on Mozilla for past screw-ups creates the impression that this statement is wrong and that both browsers are equally bad at privacy because neither of them is consistently perfect.
Even if the criticism is technically correct, piling it on like this creates a skewed impression that if you care about privacy you might as well use Chrome because even if you switch to Firefox your privacy will be invaded anyway.
This normalises the level of invasiveness of Chrome and equivocates its consistent and intentional behavior with a series of exceptional missteps.
In case you think "But I never mentioned Chrome", well, Chrome and Firefox were the only options in the original post so anything negative about Firefox implies a positive about Chrome and vice versa. If you wanted to call out specific behavior, either present an alternative (Brave? Ice Weasel?) or clarify that you're addressing the behavior categorically and not just that instance of it specifically.
If someone says "Don't use A. B is better because it doesn't do $thing" and then you respond by "I've seen B do $thing" that implies equivalence between A and B even if B did $thing only a few times out of carelessness whereas A intentionally does $thing all the time because its business model depends on it. It doesn't matter that you didn't mean it that way, it doesn't matter that it's true and it doesn't matter that this is a mistake on part of the audience. Humans are flawed and communication requires you to take those flaws into account -- unless you just want to express yourself.
Not sure relative to Safar or Edge.
Of the problems I've had with Firefox, some of them are actually due to it being _too_ privacy focused, and not having good UX explaining why common operations don't work as expected. For example I couldn't save a file onto my computer and was pulling my hair out until I did a binary search through every version of Firefox, found the first version that didn't work, read deep into the patch notes, and discovered that I needed to set the magical flag of dom.ipc.plugins.sandbox-level.