I think Firefox is by far the best of the lot, and for my purposes (i.e. paranoia) it has a lot of useful add-ons for blocking scripts, cookies, ads, and other such crap I don't want to see and don't want on my machine. Slows things down a bit sometimes, but not enough to bother me, and for sites I trust, like this one, I can customize all the settings for what I will and won't allow.
With very few exceptions, I don't like the direction software developers are going, they all seem to be taking the lesson from Apple: you don't want to know what's going on, you don't need to know, don't ask, everything will be taken care of for you. Windows 7 I find won't let me control the machine to the extent I think I should be able to, I can't even own my own applications, some bozo called TrustedInstaller owns them. Internet Explorer and Outlook are security sieves, MS Office is bloated and stupid, Windows Defender is pretty much useless, the Norton and McAfee security suites have become hogs...ah, the list is endless. I use shareware and freeware as much as possible, Firefox for web browsing, Mozilla Thunderbird for email, OpenOffice for word processing and spreadsheets, and a variety of utilities like CCleaner, Defraggler, TweakNow, SiSoft Sandra, and some others. The only commercial software on my systems, apart from the OS, is Kaspersky's security suite.