It’s kind of weird that the movie that establishes Vader as Luke’s father (albeit perhaps a clone thereof or something) also features an extreme uptick in him Force-choking officers to death.
I blame George Lucas & Larry Kasdan reacting to the mild-mannered Vader of Leigh Brackett’s draft, where he dismisses officers who fail him with mild reproofs like “Leave me, you incompetent idiot.”
I think I can agree most with your take on it. Perhaps I was a bit unclear in my original post: Vader, while he does raise his voice in a number of instances in the original movie, is given a lot more contextual cause to do so. In his own ranks, he carries the amount of respect and professionalism that you could expect a high-ranking officer to have. If the briefing room scene had been in ESB, Vader would almost certainly have killed Motti. The only times he raises his voice are against Leia and in a moment right after a failed interrogation. I’m not arguing that he was less evil in the original, I’m arguing that I think the evil was portrayed a lot more realistically.
And I have to admit, Brackett’s more mild-mannered Vader appeals to me in a certain sense. Again, my main problem with ESB is the fact that his casual dispatching of his underlings is almost played as a running gag.
At least they didn’t stick with him having a pet gargoyle or ripping Threepio’s heart out.