That's 6A[m] only, they have different properties.
6A]m[ is completely fine, it's a great move. You have a fair amount of gatlings for it (5A 2A 5B), the animation is fairly subtle and you get good damage off of it for no meter and it's essentially 100% safe. It may not be as strong as Makoto's 6B but it definitely leaves nothing to be desired.