The risk of contracting SOME disease via DATY or BBFS is probably about the same. The big difference is WHAT disease you are likely to get. BBFS is associated with HIV whereas DATY is not.
However, via DATY or DFK you could pick up pretty much any other infectious disease that the SP may be carrying, from a cold or the flu to something potentially more serious, and a there few specific STD's as well that you could get--herpes being the big one.
Perhaps the one you should worry most about would be hepatitis. Not every strain of hepatitis can be vaccinated against, but a fair number can be, and so anyone who is going to do any kind of BBBJ/DATY/DFK with random strangers should probably go and get the set of three twinrix shots (now, in one month, and in six months) that vaccinate you agaisnt at least some of them for life.
Obviously that doesn't save you against picking up whatever other random diseases are circulating. Swapping bodily fluids practically guarantees that you'll catch whatever she's got. Fortunately, it probably isn't fatal.
Scary things floating around out there, especially among some immigrant groups: tuberculosis, meningitis, etc., obviously can be picked up by any close physical contact. The risk is lower though.
Good general advice is if the SP is sneezing, coughing, or in any other way looks sick, walk away. For SP's the same advice WRT clients.