First, speed isn't everything! Don't buy a bow just because it is fast as it usually won't be as pleasureable to shoot or as forgiving. With that said, out of the two, the BK II is more forgiving while also being faster! When I say more forgiving, you have to remember that these are both bows built for nothing but speed and will lack in the other aspects that should be looked at, such as smooth drawing, forgiving, quiet, shock-free, ect..