Drupal Forum or PHPbb3?

This is really strange... I could swear I answered this one earlier today. Anyway:

I take the opposite position of MGadAllah, and I'd like to know on what foundation he puts his? In case you havent noticed, Drupal.org is usually painfully slow compared to say gentoo or ubuntu forums.

Drupal is not optimized to run forums. It's inifinitely more flexible, but it is not designed to render forums efficiently. For instance, take the front page of the forums: phpBB, and other forums, have all the relevant information ready to go in the database and can fetch (excluding little niceties) all of them in a single request from the database. The database doesn't have to look up usernames for the most recent posts etc, it doesn't even have to sort the result because the special index on the forums table takes care of that, nested forums and all. That page just literally drops out of the query cache (that is hopefully enabled), and the index page can render it very fast without loading irrelevant modules.

On the other hand I agree that, and I mention it in several places, this module is not for people who are not comfortable with developing in PHP and understand cookies etc. But that's not what the question was.

Regardless of what solution you pick, if you want really snappy pages you should put the DB on another physical box (connected via Gigabit Ethernet, crossover or good switch), tune the database carefully, have correct expiration headers on JavaScript, image files, set keepalive pretty high and preferably stick something like Varnish in front. GZIPing the output (but let the cache do it), and running something like eAccelerator, help a ton too.