U run both, basically a mixture of man, cover 1 man blitz, cover 3 but the backbone of the 3-4 and the reason why it's so good at getting pressure is the 3-4 blitz, u blitz all 3 linemen and the offense has no idea which 2 linebackers u will blitz or stunt out of the 4, the cover 1 man blitz is awesome, u blitz all 3 lineman and both 3-4 olb so it's basically a 5-2 blitz but much faster, but u have to have 2 good man corners and a great center fielder at safety at Ed reed, this is why the ravens have been so much, Suggs and reed