First, L.A. Noire and Red Dead Redemption (RDR) are two completely different games.
First, L.A. Noire is less action packed. It uses more of your brain. It has a lot of puzzles. Yeah, and it's long (3 discs for the XB360[also, that's what she said]). Anyways, the gameplay is slower than other games from Rockstar. The replay value isn't very much. At the end of the game you're stuck with your partner that follows you around and you don't have any weapons. All you do at the end is explore L.A. But L.A. Noire has a great storyline.
RDR is way more action-packed. It's a lot like GTA, if it was set in the Old West. You carry weapons, no partners and the replay value is way better. The storyline is okay. I mean, just like all of the GTA games I've played, the storyline isn't that great. The game has a sort of twist ending, but it's not that surprising. At the end though, you can run freely and shoot innocents. I would say go for RDR if you wan't action, L.A. Noire for puzzles and a better storyline.