I think you should get the Lanvin.
I think it would look amazing on you! I really like the one you have chosen. I mean, the Chanel is classic, and amazing. But, I have heard about the quality decreasing. I read an article about that, and I saw a ton of comments/threads in the Chanel forum... But it's so hard! The Chanel is iconic, and classic. The Lanvin is stunning too. But, if the Chanel wasn't so classic, would you really want it more than the Lanvin?
I also think that I see, even here in TN, more Chanel bags. I have never seen a Lanvin, maybe once. I think not everyone will have the Lanvin compared to the Chanel, and it is personally the one I would choose. It's such a hard choice though. It's your decision, but keep that in mind. I'm not sure about where you live, and which one is more common though. But have you heard of any malfunctions, or quality decrease with Lanvin?
They both are beautiful, and will both look amazing on you no matter which you choose (: