That's a question that only you can answer.
I'll answer with another question (or rather a couple):
- do you miss any functionality?
- do you have any problem with it? bugs that do not get fixed?
I have no numbers, but I think that box flux and openbox are heavier and richer window managers than blackbox. They are also very actively developed and maintained.
It all depends. If you feel that you need anything more, try telling us what you are looking for and we will try to give you some advice on what direction you should be looking. If you don't feel this way, and the answer to the two questions above is "no", then there's no reason to look for anything else, unless it's out of pure curiosity, which is such good reason (if not better) as any other.