The pre-911 mindset of "let the hijacker do what he wants and it will all turn out ok" vs. "lets rush this guy and take him out no matter what kind of weapon he has, whether or not it's a real threat" is the biggest difference IMO. Spending millions of dollars to train and equip certain people is throwing crap on the wall and hoping that it meets just the right situation, in terms of having an armed crew + the opportunity to use it + a real threat.