I've had personal experience owning both. I purchased the m/l lambskin silver hardware and got denim transfer on the back pocket as well as on the corner edge of the front flap. I must have rubbed up against some new denim while shopping and had not noticed until my friend pointed it out to me. I was utterly devastated bcs I love the feeling of lambskin. I went to my local chanel boutique and asked about redying the bag. Luckily my sa informed me he was expecting a shipment of caviar so I waited few wks and got my jumbo caviar ghw and have had it for 2.5 yrs now. Still looks brand new!!
Depending on your wardrobe you cam go with either one. It was my fault for getting denim transfer on my lambskin but if you are not the type to be extra cautious with your bag then I would choose caviar. Even if you don't wear denim...you never know bcs someone can bump into you or something.