i love both styles, but i had to vote for the city. the leather might appear to be thin, but it is durable. i don't baby my bags at all, and my city does not have any scratches nor does it show any unseemly signs of wear. in fact, it has aged gracefully considering i purchased it two years ago, have used it more than any of my other bags, and i've even worn it in torrential downpours. a big factor for me is weight. while i don't mind heavy bags (hello! my favorite bags are mj and heavier than anything), the city is so lightweight and comfortable to use. the miu miu can be awkward to carry for long periods of time because the handles are so short. the shoulder strap is not comfortable for me either.
yes, there are a lot of bbag knockoffs, but almost anyone can tell a fake from an authentic one from miles away. the fake looks like plastic and the tassels don't 'swing' like the real ones do if you know what i'm talking about. believe or not, there are fakes of the miu miu bow bags now. i saw a few on canal street a couple of weeks ago. counterfeiters will make replicas of any popular bag.
the bbag is iconic whereas the bow bag isn't. the miu miu is cute and feminine, but the bbag is more sophisticated and stylish imo. that's my two cents. hope you're able to come to a decision soon!