I think the 2nd one is my favorite, musically speaking. If you only have time to watch one of them, I say watch "We Are the Ones"...
What do you think?
Yes We Can
Plus after the song is over, wait for a bit... there are statements by the people in the video speaking about Obama and this election in their own words...
We Are the Ones
(we are the ones we've been waiting for)
There's bonus footage after this video too.