I like them both really and that is why I got the two sizes. It really depends how much you need your bags to hold. The Stam is large and the mini is more medium size.
They both weigh around the same because the chain on the mini Stam is longer and heavier. The mini Stam can be worn as a crossbody not sure if that is a plus for you.
The handles are different too. The leather handles can be over the shoulder but the mini Stam is only long enough for the elbow.
I am also 64 inches tall and 100 lbs. The Stam looks a little big on me and I think the mini Stam is more proportionate. If you are shorter maybe you want a mini Stam.
Both are great choice though! If you have more questions feel free to ask!