I've read both speeches.
Obama's is the speech of a young senator who was once a part-time law professor--platitudinous and preachy, vague and pseudo-thoughtful in an abstract kind of way. This sentence was revealing: "On the other hand, I recently opposed the release of certain photographs that were taken of detainees by U.S. personnel between 2002 and 2004." "Opposed the release"? Doesn't he mean "decided not to permit the release"? He's president. He's not just a guy participating in a debate. But he's more comfortable as a debater, not as someone who takes responsibility for decisions.
Cheney's is the speech of a grownup, of a chief executive, of a statesman. He's sober, realistic and concrete, stands up for his country and its public officials, and has an acute awareness of the consequences of the choices one makes as a public official and a willingness to take responsibility for those choices.