Different yes as was the type of combat, the location, the author and sources and I'll miss a few more. As opponents the German's were at least honorable excepting some isolated but never the less often frequent butchery (i.e. Malmedy). The Marines fought a almost entirely ruthless opponent in the Japanese
, no quit, disregard for life in the way we know it, hid and fought a defensive war after Guadalcanal, significant casualties seemed the norm. The media/press was more likely to be in Europe than the Pacific which is possibly better that it happened that way.
The strategy was to defeat Hitler first, then the war in the Pacific. I disagree that the Marines lacked honor, and as for a breakdown in the Geneva Convention? The Germans were guilty of this and many other atrocities, but the Japanese never abided by them and were not shy to say so, hard to convince your fellow warriors to abide by something the enemy disregards. The Marines ( I know Army also in the Pacific) attacked and couldn't leave or be relieved it seems until they were a casualty or the conflict concluded, troops were rotated more frequently in Europe or at least a greater attempt to do so. And to me what's most important is that one was written by Ambrose who's style chose not to dramatize the ugly or the I can't believe they did that incidents, truth is they had sex in Europe and shot German's at times when not necessary, it happened. The Marines story was told by Leckie ( not my favorite) and Sledge ( his accounts are the best). Each series needs to be appreciated for individual qualities, there are parts of BOB that I don't care for, but it is overall a better directed series. The Pacific really picks up at Peleliu and continues with a strong finish at Okinawa, but again it's just a weaker director, the stories of both are a testament to the men who fought for our freedom.
The individual soldier stories are horrifying and inspiring with human courage and sacrifice, I feel it a disservice to compare one as better, they are just different. Both series deal with real persons, each of which was affected for the rest of their lives.