Whats better?

it's really all personal preference.
i personally like the look of the first much more than the medium/city, but the first is rather small. if you carry alot of stuff, you're better off with the medium or some of the other styles (such as my favorite, the twiggy).
check out http://ateliernaff.blogspot.com/2005/09/balenciaga-motorcycle-style-reference.html for more info on styles, measurements, etc!

good luck!