The OS you use can have an effect on your browsing safety, but avoiding the use of IE can protect you from a lot of viruses that are out there these days.
you can use Internet explorer 7.0 now with tabs or firefox latest version, internet explorer 7.0 is quite heavy meaning it will get stuck if you are surfing auto surf sites but firefox deosnt so i think firefox would be better, i use firefox to works really well and the pc dont go slower even if you are auto surfing!
Firefox is definitely more secure. IE is just not secure enough, and most spyware gets to your computer through Internet explorer, as Firefox does a better job in protecting you
Firefox is more secure.
I personally prefer IE though, just because I've used it all my life, and most sites look better in IE. Although Firefox is the safer browser.