They are both nice, but I would get Medium Fendi B.Bag -- I love its style, size, and shape. It would really add 'dressed up' feeling to outfits, Paddington is more casual. As for B.Bag's trendy factor, I think a lot depends on the color & material you choose -- patent leather ones in Red/Blue vs. plain leather (or some patent on leather) in neutral colors like black & tan.
B.Bag is a statement bag. =)