They're both rubbish, (though McCain's is much, much more tasteful imo) but I think they're an interesting example of a difference between and .
In McCain's video, the focus is on looking back at history in order to inspire a sense of duty, and determination, and honor. It mentions unyielding, never giving up, the idea that evil "must" be vanquished.
In Obama's video, a major element is the crowd, and getting you roused and in the mood. The "chorus of millions". He mentions the change happening between two distant geographic points, giving the impression of a widespread revolution across a vast distance.