The new guy brought a very different tone to Dumbledore that was not conveyed in the books. He expressed anger at times, as seen in the above image, which is very un-fitting. He didn't have the serenity and composure you expected. Dumbledore's benevolent personality was essential to match Voldemort's pure hatred, especially because he was the only wizard that Voldemort ever feared.
It wasn't that anger is unfitting of Dumbledore. It's that, as you said, he carries himself with serenity and composure; when he is angry or disappointed, he uses a soft, reasonable speaking tone, rather than shouting and flailing about as the replacement did.
I also disagree with Ravyn that the first Dumbledore sounded weak and sickly. He was elderly, yes, but he had a vigorous spirit that shone through the frail shell. I always got the feeling that if he were forced to face Voldemort, he would win without so much as batting an eye.
