GM was pretty big, i tried it on at the boutique today....everyone agreed that it was just way too big to be worn as a messenger. it's cute to be worn as a handbag or on the shoulder with those shorter straps though.....
so i came home with MM, it fits quite a bit, much bigger than musette tango.
i had my rose NF today and most of the things in my bag went in the GM ok..... my pochette wallet, small ring agenda, pochette w/ all sorts of crap in it, camera, 4 key and cles, 3 diapers and bag of wipes....and oh, my iphone. and it didn't even get bulky and stayed pretty nice and thin.
but i wanted a messenger and i'm pretty happy with MM size --- for now. =)