Bowlines fail because they can untie themselves. Fig-8s don't (except if tied as an EDK, when they roll even with really long tails). The only complaints about Fig-8s is that they are too hard to untie when projecting sport routes, or that they make you look like a n00b because you have been tying in with a bowline since the days of PA's and you are too oldskool to change and get safe.