BOB is just fantastic, start to finish, Pacific, I don't even think its good, theres an episode or character or actor in there I liked, but for the most part, it really wasn't good. High budget, pretty in terms of filming and what not, but the character interaction, which is what makes BoB what it was, just isn't there, at all.
Why they did it I really don't know, they should have picked probably another campaign in Europe, or whatever really, the Japanese/Pacific conflict is just brutal, its too brutal to have the lighter hearted bits that helped build and portray the characters. BoB made you feel exceptionally bad for the guys going through it, Pacific just built up the guys as almost monsters that you didn't really care that much for.
The other thing was the attacks/assaults, the action in Pacific was poor, again techincally accurate, well shot, woo, but it was basically either stand firm and shoot at tree's then see a pile of dead bodies, or hide in a mud puddle behind a hill , mortor something, shot some civies and then Japanese run at you like psycho's.
The one more open field thing they did, the attack on the airfield felt, wrong, it almost entirely focused on a the American's, as in, 90% of the action was American's running at camera's.
I don't know if they were going for a specific style, wanted it to be ultra brutal, or wanted the characters to be hardened soldiers.
Start to finish BoB is epic, great cast, great characters, great writing, great campaign, great stories, great battles, great emotion, good pacing, good understanding of how bad things got, and showing a lot of the lighter moments, the training, and the chilaxing after the war was won.
Pacific was poor stories, poor characters mostly, only really 2 or 3 great cast members in the whole series, poor pacing, poor battles, and thats about it.