Out of the two I definately prefer band of brothers. The weekend before The Pacific aired they showed the whole series over 2 nights, had been years since I last saw it and was yet again engrossed.
Aside from Leckie, I have no real feeling for any of the characters in The Pacific. It seems like they were trying to go for the awesome heros angle straight from the word go. We wern't introduced to dyamic people so much as "ooh rah we're the marines". Which I guess is great for Americans but as a Brit the marines...how to put it without sounding offensive. It would be like an average American watching a series about a squad of Royal Marine Commandos, they mean nothing in your own culture, so you don't understand why they are often made out to be one dimensional badasses.
Perhaps, again, as a Brit I can identify with the warzone of BoB more, like with Saving Private Ryan, even though the story focuses on Americans, you know a few miles up the coast British/Canadians were facing the exact same carnage as they stormed Sword, Juno and Gold beaches.
It should be said though, I'm still very much enjoying The Pacific as a series.