Forget security as far as browsers are concerned
Browsers just display web content on your PC. Some browsers do it faster than others.
Hackers load virus and malware in web content such as a Flash images or videos. Some sites are notorious for infected content. Hence WOT and programs like spywareblaster that will block the site from openign in your browser.
Your antimalware. antivirus and firewall are there to block these things being download if detected. So if you have good security there is no need to worry.