Chrome is run by an ad company with a vested interest in your data and has been outspoken about banning adblockers in the past.

Firefox is a completely open source project run by a non-profit organisation who accepts donations to cover costs.

Other Chromium-based browsers can generally be fine but the overuse of chromium reinforces web standards that are hard to reproduce. A web browser is a fairly complex beast these days even for the best programmers. Just see XMPP for an example of where things could lead to.

While it's true that Firefox receives some of those donations from Google for being the default search engine, they have no influence over decisions made by the Firefox team whatsoever. That's the short version of it.

As I understand it, you can make a Chromium browser just as privacy friendly as Firefox. I use Vivaldi on my home PC and mobile which is strongly privacy focused and has a ton of small QoL features neither Chrome nor Firefox has (I use both at work, prefer FF over Chrome). (Going off the tangent here) for example, it's incredibly easy to re-open recently closed tabs in Vivaldi with just two clicks—a feature I use all the time—as the recently closed tabs list is very obvious and easy to access in the tab bar itself without the need to futz around in the menus to find browsing history. The customizable speed dial, sidebar menu for things like bookmarks and downloads are really nice and the download manager in Vivaldi is IMO better than FF, too.

The bigger problem is Google having defacto monopoly over browser market and thus having too much influence over how web standards work and how the user can browse the web (I'm old enough to remember "This web page is best viewed on Internet Explorer" messages on websites). The move to manifest v3 to curb content blockers is one such example.

I'm sure you can just Google what the benefit of using Firefox is. When "privacy" is talked about in terms of web browsers and apps, it's mainly about blocking trackers. Ad companies inject trackers into websites and apps, which collect your data. Google has their own ad company, and by using Chrome, you're supplying them with personal information without them even having to pay. Firefox doesn't sell your information. They also have many extensions available that will block any data collecting attempts from websites.

Duck Duck Go is even more secure. The whole point of their browser is for user privacy. Their app even blocks other apps from tracking you. You'd be amazed by the data collected by apps. My fucking shopping list app has trackers from multiple companies.