Honestly, the OS (operating system) probably matters more than your browser for security. Windows is hard to secure and you would be better off running Linux or Apple OS X if you want security.
There are two things you need to look at for browser security: 1. how good is it at keeping out bad guys and malware; 2. is the browser phoning home private information about you to it’s maker or some third party, where that info becomes a temptation for governments on fishing expeditions.
Here are my choices for relatively secure Windows browsers:
Comodo Dragon – I like this better than Google Chrome. It is very similar to Chrome but does not phone home to Google. This is basically Chrome without Google looking over your shoulder.
Ice Dragon – also by Comodo. This is Comodo’s security enhanced version of Firefox, and allows you to use Firefox extensions.
Epic Privacy Browser – (available for Windows and Mac) I will refer you to the website to explain what Epic does to protect your privacy. No system is bullet proof but this is a step in the right direction.
Opera – my old standby.
Note: All browsers can be made more secure by turning Java script off.
No browser is 100% secure. With Windows always use an anti-virus program to protect your computer.