The Pacific seemed to be more about the individuals struggle with war and the torments that it scars the soldier with, whereas Band of Brothers was more about the bonds that grow between soldiers during war, and how those relationships form and evolve.
I think both accomplished their goal, its just that Band of Brothers works so well because we grow attached to the company and we are experiencing these relationships form and change with them, and the heartbreak or joy when something happens. Whereas when we watch the Pacific, we still feel a profound sadness for what we see, but we know its just a TV show and its hard to put ourselves in their shoes and imagine the kind of hell they have been through.
However, the biggest flaw in Band of Brothers is that there are so many characters that it takes more than 1 viewing of the series to become totaly comfortable with who everyone is, and by that point, the suspense and drama of not knowing what happens to them is ruined, even though there are some scenes that will break your heart everytime, example, knowing what happens to Toye and Wild Bill in Episode 7, I dread having to watch that part. Still, if I cared about them as much as I did during the first viewing, it would have made all the more impact on me.