Stock. I've tried them all, but at the end of the day, no need for anything else. Just never saw any functionality gains that I actually use.
Dolphin was a close 2nd, especially with the add-ons
I actually didn't mind Bing
Skyfire was better on my old windows phone.
Opera and Miren were nice, but nothing special
Firefox was the worst of all of them and I use Firefox at home and work. Such a dissapointment