TLDR - Firefox takes the best of all worlds and is top tier in all sectors - it's arguably most private, secure, ethical and performant browser. Other browsers may be slightly better just as good in one category, but Firefox is best or tied for best in each category. Brave is just as good with privacy, but is unethical and slightly less performant and secure. Chrome is less ethical, performant, private and slightly less secure. If you're a Chrome user, you should at least switch to Chromium.
Google created and maintains a browser called Chromium. Chromium is open-source, meaning you can look at all its source code and change it if you'd like. Chrome is a modification of Chromium; Google essentially takes Chromium and adds its Google branding to it, then releases it as a closed-source browser called Chrome. Brave is another browser based on Chromium that is maintained and created by Brave Software, Inc. It adds features like ad-blocking and BATs, which support content creators with anonymous ads. Firefox was created by a bunch of volunteers who came together and created the Mozilla Foundation. It's the only major browser that is not based on Chromium (with the exception of Apple's Safari, which is a great browser that unfortunately only works on Apple devices).
Chrome, Chromium and Brave are all compatible with Chrome extensions. Firefox has less extensions, but more than enough to cover most commonly used extensions, like ad-blockers, dark mode, Grammarly, and others. If you're thinking of switching to Firefox, you can check if the extensions you need are in the store. With the exceptions of BATs, most features are the same.
Brave's BATs explained: Brave wanted to find a way to support creators while still having a private browser (typical ad services will track you in order to personalize your ads). To solve this issue, Brave has an optional feature that allows users to view anonymous ads inserted into a webpage by Brave. Brave then gives the ad revenue to the content creator (the author of the website you're on) in a cryptocurrency created by Brave called Basic Attention Tokens. Less than one million content creators have signed up to accept BATs as payment - right now, it's chump change. I personally think it's a great idea and executed well, but it's only available on Brave Browser right now. If BATs became supported by Google and became integrated into Chromium (which is very unlikely), I think it would take off.
Another feature which is cool but not useful - you can write your own CSS to customize how Firefox looks. Look here.
Chrome is indisputably the worst browser when it comes to privacy, and it's no surprise. Ninety percent of Google's revenue comes from advertising. How does Google make so much money from advertising? Well, every time an advertisement from Google is clicked on, Google makes money. Google maximizes profit by tracking you across the web. For example, a painter could be looking at a lot of painting websites, so when that painter is on a webpage with ads, the painter will likely get most or all ads about painting, even if they're just reading the news or using websites not relating to painting. In this context, privacy means stopping Google and other websites from tracking you across the internet. So if that same painter used a privacy respecting browser like Brave or Firefox, they'd be getting ads only relating to the website they're on - paint and colored pencil ads on art websites, ticket and sports betting ads on sports websites, and Viagra ads on Trump supporter websites.
If you're a Chrome user even slightly bothered by Google knowing everything you do online, you should switch browsers. If you enjoy Chrome's look at feel, you can install Chromium. It's a good idea to install some privacy related extensions as well.
Firefox and Brave both block trackers by default. Brave also blocks ads by default, with a built-in ad blocker, while Firefox offers a list of extensions it recommends to help block ads (Brave actually brags about blocking ads by default, compared to Firefox and Chromium where you have to install an extension, it's terrible). Both are equally as good from a privacy perspective. Many people argue that, because Brave blocks ads by default, it's a more private browser, but the privacy aspect of ads is about the trackers they come with - Firefox shows ads but block trackers, which means it's just as private as Brave or any other browser that blocks ads. Personally, I use an ad blocker with Pi-hole, which blocks ads on a network level.
One thing in particular that bothered me was how Brave blocks Carbon Ads by default. Carbon provides privacy respecting, unintrusive, and lightweight ads. These are anonymous ads that have no trackers which support the content creator. If a creator wants to make money from Brave users viewing their content, they have to sign up for Brave's BAT program. In my opinion, this is terrible. Brave essentially blocks ads from an advertising provider with the same core principles as Brave. There's nothing different about Carbon Ads and BAT ads (with the exception of the currency the content creator is paid in), so Brave, the browser that's all about privacy, blocks privacy respecting ads, and takes revenue away from the content creator, forcing them to sign up for the BAT program if they want to make money from Brave users viewing their content, even though Carbon Ads and BAT ads are essentially the same.
Firefox and Brave are the winners here, both are just as good as each other in this category. Chromium is next, as it doesn't track you, but it allows websites to pretty easily. With the right extensions, it can be just as private as Firefox or Brave. Last place is Chrome.
Chrome and Brave are both Chromium-based, so Chrome and Brave are both subject to the same security vulnerabilities that Chromium has, which means I'll only go over the security vulnerabilities in Chromium. To determine how secure a browser is, we need to learn about its internals. Firefox and Chromium were both initially implemented in the C and C++ programming languages. The problem with C and C++ has to do with how they manage memory - programmers have to manually write safe code, which makes it easy to make errors that can lead to an exploit. In 2015, Mozilla came out with a new programming language called Rust, which is programmed in such a way almost every memory management error will result in the code not being compiled or compiled with a warning shown to the developer. This is called memory safety, a feature in Rust but not in C/C++. So, a program written in Rust is much less likely to have memory vulnerabilities than a program written in C/C++.
Both Chromium and Firefox have public bug trackers, which we can look at to see vulnerabilities. About 70% of Chromium exploits are related to memory safety, and we can assume the same proportion in Firefox. Mozilla is trying to make Firefox a secure browser by converting the source code of Firefox into Rust. Right now, it's only about 12% of all the Firefox source code, so the Rust conversion hasn't made Firefox the indisputably most secure browser, yet.
Overall, 12% of code conversion means that Firefox likely has slightly fewer security exploits than Chromium, Chrome and Brave. Overall though, the difference right now is so marginal you don't even need to consider the security differences.
Something to think about: Why isn't Brave based on Firefox? Brendan Eich co-founded Mozilla, which created Firefox. In March of 2014, he was appointed as CEO of Mozilla. At the time, news came about that he made political donations in support of banning same sex marriage in the state of California. Because of this, Eich was met with a lot of opposition. Eleven days after being appointed CEO, he resigned, stating "under the present circumstances, I cannot be an effective leader." Later, Eich founded Brave and decided to base it off Chromium. That begs the question: does Eich think Chromium is more secure, or was the decision influenced by contempt for Mozilla's Firefox? Of course there are other factors, like Chromium being compatible with Chrome extensions and getting new web features faster, (for example, Chromium had Bluetooth features implemented before Firefox) but those aren't significant factors as Firefox has a wealth of abundance of extensions as well, and new web features aren't needed to be implemented faster, as web developers usually wait for new web features to mature before using them.
Another thing to think about: Why is Tor based on Firefox? For those who don't know, Tor is a browser used to access the dark web. The Tor Network uses a bunch of types of encryption, proxies and other protocols to make sure your browsing is private, secure and anonymous. That begs the question, why did the Tor organization decide to base the official Tor browser on Firefox? Is it because they believe it's the most secure, private browser, or any other reason? It could have been done with Chromium as well, as Brave has implemented connecting to the Tor Network in their browser.
First, let's go over a comparison of RAM usage. This is significant to those who have low spec'd computers and those who like to run a lot of applications at once. For those who don't know, RAM is where the variables in a program are stored. Using excess RAM can slow down your computer, the browser itself or other programs. If you run out of RAM, other applications can't run. So, let's look at the RAM usage. Here, we can see a comparison in this article, showing that Firefox consistently used more RAM than Chrome. There has not been many legitimate tests of Brave and Firefox's RAM usage being compared, but it likely is slightly less than Chrome because they are both based on Chromium, but Brave blocks ads.
Second, let's go over a comparison of page load times. Brave typically does well on websites that have a lot of ads, because it blocks advertisements on a browser level (using native code, which is faster) and not using an extension like on Firefox or Chromium. This means that Brave will typically do better on pages with a lot of ads, ex. any Forbes article. However, I was surprised when I saw this benchmark. Unless you're loading many pages a minute with a lot of ads, Firefox is generally a bit better in page load times. For page load times, Firefox and Brave have small differences. Chrome, however, is slower.
Firefox wins here, but if you have a new or fast computer, you needn't worry of this.
Also, Mozilla, the creator of Firefox is nonprofit. Brave Software, the creator of Brave, is for-profit. Obviously, Google is for-profit as well.
In addition to that, Brave's co-founder and CEO is homophobic, as stated in the security comparison of this article.
Firefox wins here, but this really is not a huge factor to most people.
You can't go wrong with Firefox. It's tied for first or first in every category. It's easily my top recommendation. If you're going to frequently go to websites with an abundance of ads, Brave is good choice as well (or, any browser with a Pi-hole). If you want to have your every move tracked, use Chrome. If you don't want to be tracked but you like the look and feel of it, use Chromium, preferably with ad-blockers or tracker-blockers. Chromium is almost identical to Chrome from the user's perspective. That's it. Feel free to add your thoughts in the comments below.