It boils down to why you want to spend time talking on a message board. Some folks like "entertaining" exchanges that get very heated ... sort of like the Jerry Springer of scuba. Others prefer to discuss things more politely, or are sincerely looking for specific types of information ... they'd prefer to feel like they can participate without the risk of getting beat up for saying something someone else doesn't agree with. Moderators will be more or less desireable depending on where in the spectrum you fall.
I prefer a well-moderated board. It provide a friendlier, more informative environment. I'd rather discuss than argue ... it's easier for me to come away from a discussion admitting I learned something new than it is simply dropping the discussion because I'm being beaten up by someone who doesn't see things the same way. Even when you disagree with someone, it's more fun (for me at least) to use persuasion than argument ... and less difficult to occasionally have to admit that, after all, the other person is right.
I enjoy this place ... lots of knowledgeable divers here who are interested in exchanging views about their passion rather than arguing all the time.
To respond to the initial question ... I think there are other boards out there just as good, but more "localized". I am very active in one that focuses on diving in the Pacific Northwest. Like this one, it's very moderated (Popeye wouldn't like it much) ... more so even than this one. But because it's so moderated, there's no spam and no arguments. It's focused, fun, and very active. We often have group dives and get-togethers ... and I've made quite a few friends and dive buddies through that board. The moderators do an excellent job of letting folks carry on discussions about scuba, while keeping the community a friendly place to play.
This board, on the other hand, gives me the opportunity to see how folks in other parts of the world view things. Different diving conditions tend to spawn off different mindsets and approaches to the activity. I may not get a chance to dive with all that many folks in here ... because we're so geographically separated. On the other hand, when the occasion arises for me to visit other parts of the country (or world), it increases the opportunity for me to find someone to dive with in a place where I otherwise might not know anyone.
I haven't ever visited alt.rec.scuba ... I've heard enough about it to know I wouldn't like the place all that much. Not that it's a bad thing, mind you ... but just that it's not my taste. Likewise, I'm also not much into Jerry Springer or the National Enquirer either. I like the saying "whatever floats your boat" .... this place floats mine just fine ...
... Bob (Grateful Diver)