NZB began life as a phpBB forum, went to IPB, then evolved to
vBulletin.
Each has its place.
phpBB doesn't have most of the functions vB does as standard, and the hacker that made the calendar/private message folders/other enhancements is French, and IMO, a rude prick...and the hacks wipe out so much standard code, installing other hacks becomes impossible.
IPB was better, but the community were a bunch of (so it seemed to me) petulant children.
The vB community on the other hand, are mighty helpful and, for the most part, capable of carrying on a mature conversation.