Both boards are useful (depending on what your purpose is). Broadway World seems to attract a younger group - probably because of the more leniant moderation, but both seem to serve a pupose in their own way.
I've been a member of ATC forever now, and if you've followed the board for any length of time - you come to realize the posting "parameters". Straight up theater discussions in a mature fashion are not going to get you banned. A lot of industry people, media outlets, etc... read the board, so I've always understood why it was more heavily moderated. Cuts down on the immature postings, but the elitist attitude of a lot of posters there (well, and here!) is a topic for a whole other discussion
As far as the ATC layout, if you choose the "flat board" option at the top, it's not much different than the Broadway World layout. Threads are bundled. The regular view can drive me crazy though.
However, I'll take ATC's dinosaur-age format all day to the format here that allows page-long ridiculous signatures that take up so much room in threads.