This subject is not simple.
I use Iceweasel 3 which is a rebrand of Firefox. Mozilla, the company behind Firefox, released the source code to the public as open source which is a really REALLY good thing. However, the idea of releasing this source is so that each user can adapt it to his or her own needs. When Debian (The distro I use) began applying patches, Mozilla demanded that they get all patches approved because "Firefox is our product". This violates the Debian Social Contract, so rather than have to ask permission to patch the source, they simply stopped using the Firefox name and logo.
I love Firefox/Iceweasel for the plugins. I'm absolutely addicted to them. I hate just about everything else about the browser, first and foremost being the fact that it isn't a native GTK application so it's always "slightly" out of place and I like my applications being uniform and consistant.
Epiphany has the sexiest font rendering I've ever seen, but it's a very basic browser. Recent versions also use the WebKit rendering engine and I'm a huge fan of WebKit. If Epiphany-webkit could use Firefox plugins, I would drop Firefox itself in a heartbeat.
Midori is a nifty little browser, especially for older PCs or embedded devices like my phones. It uses WebKit too.
In short, I picked "other" because there is no single browser that does everything well. I regularly find myself bouncing around for some experience or another.