Bottom where everything else should be as well for any other apps since it’s much easier to use, since like everyone has said phones are getting huge these days.
Switched it to the bottom only to find out it didn't matter one bit and was still just as hard to reach there as it was at the top. Moved it back to the top because that's where my brain looks for it.
@someguy3 Top. Tried it on the bottom, didn't like it, since I kept fat-fingering the OS navigation button bar, and I've gotten too accustomed to the top position. Also use Firefox on a Galaxy Tab, primarily in landscape mode as a mini-laptop with a keyboard and mouse, and top menu feels more natural.
After using the bottom bar for just a few minutes I don't want to ever go back to the top bar. Honestly, I can't comprehend how it isn't the standard for mobile browsers. It seems to make quite a lot of sense to put UI elements where they can be easily reached...
Keep it at the bottom, that's how the old Opera browser had it back when it was one of the first mobile browsers and it's always felt completely natural to me since.
Top. Thinking about it, I feel a vague sense of dread anticipating the day Mozilla decides it should be the same for everyone and removes the option, as is their wont.