Board Thread:Help Board/@comment-27072805-20151023151327/@comment-26021614-20151025044453

BB Atk boost will boost your attack only if you use BB/SBB/UBB.

Atk boost will boost your attack no matter what attack you are using.

In theory Atk boost is more effective because you don't need to use BB/SBB/UBB, but most of the time BB Atk boost is a higher boost, making it more useful.