Another big difference is that President Bush was at the front end of the war and needed everyone in the public to be super pumped for going in and killing terrorists, whereas Obama is at (we hope) the back end of the war and needs everyone to remain positive about getting the troops home, which, if you're a media leech and want to make the best case for bringing troops home, involves a lot of NON-smiling troops. If you're a member of the media trying to sway public opinion towards ending the war, you're not gonna show a happy CinC in front of a bunch of happy troops; you're going to show a serious CinC in front of a bunch of troops who are pissed off at life and want to get the fnork out of the damn desert.
Just my $.02
PS I nominate Brett for VP of Political Sanity.