There may be some overlap, but they have different focuses and are more different than they are the same.
BTT focuses on enabling and customizing your input devices to activate more things.
KM also has some functionality in the area of input devices, but not as much as BTT. KM excels in the types of action based workflows it can produce, and these are well beyond the options available in BTT alone.
Together they are also greater than the sum of their parts. 