I never judge metal bands on their technique based solely on their live performances. In live situations most of the time the performances get buried from the overwhelming bass frequencies and overall volume and while sometimes you get the general outline of the riff or the song you hear it's impossible to hear the detail of each individual performance. In my opinion when playing live you can get away with extremely sloppy playing and people won't be able to tell. That's why I generally don't really enjoy seeing bands playing live.
But you're probably talking more about the energy, the image and the "movement" of the band on stage, which is another matter.