MyBB or Phpbb? Which should I use?

 

phpBB, because it is a lot more common and has a great community supporting its development.

 

Actually--I know from experience--you should use neither.

I have been using SMF for a number of years now, and it is definitely my favorite. It's easy to customize, and has an easy-to-use theme and addon architecture, so you don't have to worry about not finding enough 3rd-party support.

One of the best features about SMF, though, is its stability. It's very fast, never has errors when installed correctly, and is VERY secure. On top of that, it's free.

Good luck! Believe me: SMF is the #1 free forum... in many ways, even better than the best commercial choices!