This question comes up from time to time. The "better" option is going to go be whatever fits best with your desired functionality. Both IPS and XenForo offer demo versions of their software. This gives you the ability to try before you buy.
All that being said, you are asking on the official phpBB site - we're going to be a little biased.
You would be much better off doing your research and picking the software that you think is best. There's plenty of options out there, free and paid.