Careerealism has a good article out today about the BeKnown and BranchOut. Their advice to would-be users is:
The BeKnown and BranchOut Facebook apps have very similar abilities, but the designs are quite different. I think your best bet is to try both and see which one feels most user-friendly to you. Why? Because it doesn’t make sense to use both. As a career coach, I would rather see you pick one and use it consistently then spread yourself too thin by using both. These types of networking tools are only good if you actually use them – so the decision as to which one you find easier to use must be a priority in when choosing which one to invest your time in using.
Apparently they have looked at both and will be offering a webinar on Thursday, June 30th comparing the two. Go to the article [Breaking News] Facebook Career Wars Are ON! to learn more and register for the webinar (or sign up to view later).