Tomb Raider: Anniversary or Underworld?

Okay so I've played just about all of the Tomb Raider games on Playstation one and two and also Wii. I don't have any of the games now because I've sold them. now I'd like to revisit either Anniversary or Underworld. I've played both and enjoyed both, but for some reason I'm leaning more towards Anniversary. So which one should I get? (This is on Xbox 360 by the way...) Thanks!