Your a lot safer on Firefox than Safari actually.
1: In hacking contests, Firefox, IE and Chrome are challenged and issues found and fixed. Safari 6+ requires a Mac and many hackers don't want to bother owning another machine just to hack Safari.
Probably the worst thing to have is to use a browser white hat hackers are just ignoring.
Also Apple doesn't allow certain things to occur on Mac's that can be used to hack, like packet injections, so the Mac is not appealing to hackers in the first place.
2: Firefox and Chrome get extremely rapid fixes, in fact mere hours after a hacking contest ends there is a update for Firefox.
IE and Safari group all their updates at one time, thus leaving exploit unfixed for months (or years) before a large patch issued. Some suspect they then can be used by convert software used by governments to spy on people like what occurred with Finfisher and iTunes.
3: Firefox is used as the Linux operating system browser of choice, and super smart geeks use Firefox and thus need a more than average secure browser and smarter designed browser than what's available from others. For instance Firefox is the only browser that stops the HTML 5 exploit from filling hard drives until the machine refuses to boot up. Despite this exploit being widely circulated, there is no patch for Safari yet.
4: Apple trys to keep going it's own direction with Safari, but with a continuous shrinking market share they are just being ignored, thus it's likely best you use Firefox for everything to be compatible.
5: Good thing about Firefox, is it's truly cross-platform. Linux, Windows and OS X, so many IT departments rather have people use Firefox and thus reduce support calls. Also Firefox is very highly customizable, with the MOST add-ons and some not on any other browser (like NoScript protection)
Nothing wrong with using Firefox, your not being "anti-Apple" for using it, it's used by many of the regulars here in fact because of all the suspicious links we tend to click on here that people post, thus the Firefox protection with all it's add-ons.
https://www.mozilla.org/en-US/firefox/fx/#desktop
https://www.mozilla.org/en-US/firefox/customize/
Because of Firefox's customization and excellent add-ons I've written two user tips to help people where Safari fails.
Web browsing for hard of seeing users
Maintain some level of privacy/cookie tracking