Skyfire by a mile! LOL So much faster. I like that it actually works to identify itself as a desktop browser so I don't get mobile web sites on my EVO.
All of them have that capability.
I don't like Skyfire, it's buggy, it fails to play Flash videos quite often (and why bother when we have real flash now anyway?), and the UI is annoying.
I want to like Firefox, but it needs to be a bit faster, and support Flash.
I use Dolphin, and really like it.