The 40 is very big! It is good for over night.I have put 2 pairs of shoes 2 pants and 4 tops plus make-up bag .I am 5'10" with out shoes.I love the Kelly 32 for everyday, too! However, since I am short I prefer to have 32's in darker or more neutral colors. With brighter colors, I'd go with a 28.
Anyone have a Birkin 40cm? It's huge but if you're about 5'3" and above it would make the most stylish carry-on!