i have to admit i know next to nothing about calfskin and lambskin (i only learnt about lambskin from my friend who's into chanel bags). but i did get to touch both the cannage drawstring in lambskin and in calfskin. i didn't know it at that time though, and i just felt that it was odd that the tan coloured cannage was much less softer/flimsy than the bright red and black ones. at that moment, i thought that i really did prefer the tan cannage's leather better because it felt like any regular leather, but just a wee bit softer/slouchier perhaps. the other colour cannages had leather that i felt was too soft for my liking. it felt very very fragile.
it was only after browsing on the dior website some time later that i realised that the tan was made of calfskin, and the others were lambskin. so i guess i prefer calfskin more (i'm a klutz, i'll probably rip a hole in the lambskin if i had one)!
and from the chanel camp, it does appear that the lambskin is really really delicate.