When I watched the first The Pacific for the first time, I couldn't help but be disappointed because I had compared it to BoB.
After a second watch I enjoyed it a lot more because it is different to BoB in that it relentlessly displays the horrors of war and how it can change people (in this case, the three major characters).
There were a couple of disappointing episodes (Melbourne, Iwo Jima), but as soon as the focus turned to Sledge, The Pacific became top notch for me.
Band of Brothers is still better because:
1) The story itself and the characters are much more interesting, and you got the interviews from the war vets themselves, which was fascinating.
2) It focuses more on the cameraderie of war, so you get to know and care for the characters, so when they fall it hits you. I just didn't care about Robert Leckie and Basilone or their stories.
3) The story follows the European Theater which was much more relevant to us.
Edit:
Just thinking now, had HBO done The Pacific in 2001 and Band of Brothers last year, would they have turned out any different, assuming they used the appropriate technology at the time?