i'm also trying to decide between the small and medium super pro, i'm a girl, 5'6" 110 lbs and I'm using a timbuk2 (classic?) in a Medium. That size is pretty comfortable, and I've tried the medium baileyworks on at my LBS, but without seeing the small i'm really unsure. the medium is comfortable on, and doesnt seem like overly big if i dont want to pack my whole life into it and just walk around (i live in boston)

does anyone have both? how much smaller is the Small compared to the medium? the measurements online don't really help.