Its always great to get everything in a purchase.... but IF id HAVE TO Id rather get the bag WITH authentication card! you can always use another box to store it... but having the authentication card.. is important, in my oppinion! Hope that helps! 

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I personally don't like the Jumbo just because I think it's too big. But I also don't carry around that much stuff.. so I guess that also contributes to the reason why I don't like the Jumbo too much. For me, the medium is the perfect size. It can be casual but it can also be used for the night out.
I think red is usually really hard to come by. But if you do get your hands on a red flap then DEFINITELY go for it!!!
I like black because if it gets dirty you can't even tell!! hehe
good luck! and keep us updated on what you decide to get