I'm of the opinion that "yellers" are never the best type of leadership example. Case in point, in my department we released two ineffective team leaders for their lack of production and inability to lead, including areas like coaching and development. They led (or tried leading) by fear, and yelling was their choice of channel, rather than a calm, composed demeanor.
It's my opinion that if someone is a constant yeller, they tend to lose their audience and become someone everyone eventually blocks out. A true leader is great at developing their peers with a composed, yet confident demeanor, and only when things get severely bad should yelling be considered. That way it creates that "holy shit, boss is madddd.. we should probably make a real conscious effort to do what he/she says yada yada yada" sense.