I like Dolphin because of the tabs. And Matt just introduced me to Miren which is quite nice. It also has tabs.
Really to me a browser is a browser, but the stock one gives me issues with the frames here, so if I use it I have to use lite mode most of the time.
I don't like the fact that I am using space for other browsers but I'm sure they don't take up much.
I realize this isn't really answering the question, but they all work usually and it's just the small features that make you pick one over another.
My killer feature will be when one lets me sync my Chrome stuff from my computer to my phone. When one gets that done right, that will be my browser.