Lanvin is nice, but Chanel is more timeless IMO. I would wait for the Lanvin to go on sale (as many Lanvin bags do, sometimes even to 60% off), and keep the Chanel. Unless you never use the Chanel. If that is the case, then definitely sell it for a bag you will use, but I would still consider another Chanel over Lanvin. Since Chanel bags are so hard to find on sale, I am getting really picky about what I buy from other brands and try to wait for sales on other brands since I know I will have to pay full price for Chanel.