I like the old board because I'm interested in a lot of subjects and I like seeing them come into 1 place and the Posts and Follow-ups are 'bulleted'.
I've been here for over a year myself as have a few other 'regulars'. As Henry says, it's easier to view the posts on the Old BBS. Like KristyH says, the time line format is good. My $.02 says that if you polled the Posters, they'll say that posting their question to a SPECIFIC subject is easier because all they have to do is go to the subject and read their follow-ups. On the other hand, if you polled the Follow-uppers, they'll say that it's easier to read posts on 1 WEB page because they read ALL posts. And the latter is for reasons like, "I want to learn more, I can't stand all the 'clicking' around, and Hey, I know the answer to that post." And so on. So, although you will get different answers from the Follow-uppers, you'll get some disparity among the 1-timers too. It's a tough call.
I know what it's like to get into custom programming but if you want the best of both worlds, maybe you have software or can write it, where a Poster MUST enter a category-field when the Post a message, where their message would get posted to a category-specific URL as well as a general one. And, at the same time, us Follow-uppers can either view a category-specific BBS as well as an 'old-type' BBS like this one. You don't need to double-up the data; just the links to them. (Hopefully I'm being clear with my suggestion.)
Again, sorry for being late for class. ;-) I was eating lunch. My best to ya and hope this helps.