Neither one meets the FBI standard of 12". 4" of penetration is frankly pathetic. The key here is remembering that while 4" may stop someone hit straight, if it's a side hit, or goes through an arm first, or a leather jacket, that's not even going to get close.
I'd say that 10" of penetration with three discs slugs is quite sufficient. I was wrong about the BBs it's 6" and I think at that point the issue has been taken care of.
It actually has 12 BBs as opposed to three that I stated earlier.