Using Firefox on Windows, it doesn't come with malware and I am very selective about add-ons and sources. No Flash for example. If a site insists on a Flash player, I don't need to see it. Using Chrome for managing my Google account and running Chromecast web apps.
Using Safari on the Mac and all iOS devices, with Chrome as a backup browser for those sites that want to do a little bit more than Safari allows, like running Chromecast web apps, though iOS has dedicated apps to most of the web stuff I want to send to the TV screen.
Explorer and Firefox have common roots in the academic predecessor to Netscape (I think of them all as Mozilla) and while each has evolved in its own direction and bloated themselves in different ways, with common roots come some common weaknesses, which is why anyone pushing a new browser tries to tell us it is a "fresh start." They all have to work with the same web protocols, so by the time you get done a lot of it has to be the same. Main advantage of a "fresh start" browser like Safari is that the development team has a better chance of knowing what all the code is supposed to do, rather than having huge pieces of "don't touch that, it's heritage and nobody understands it" forcing you write a new piece to do almost the same thing with a few additions.
Been there, done that, about 15 years trying to maintain and enhance large mapping and GIS codes, while at the same time doing "fresh start" systems to accomplish the same functions on radically new computer computers, graphic workstations replacing batch jobs on mainframes.
Firefox works well enough on Windows that I don't accept Apple's offer to download and install Safari, as well as it works for me in the Apple environment. Too much mixing of user interface metaphors. Which is also a slight problem sometimes bringing Android UI apps like Chrome into either Apple or Windows environments, but Windows keeps changing anyway as MS tacks on Abndroid and Apple features.