It depends. Tuco, Gyp and Richie are guys that burn hot. They are very disturbed, extreme individuals, and are prone to doing extremely fukked up shyt when their blood is up.
Chris Partlow burns cold. He doesn't take joy in atrocious behaviour. He just does what needs to be done, like a robot. Emotion doesn't enter into it(with one exception, we all know which one).
It basically boils down to that old question: which is scarier, the killer who takes pleasure in his work? Or the killer who simply doesn't care one way or the other, who will kill a person with as much emotion as they would order a coffee?