Good to know - thanks! One of the main reasons I always need a larger bag is because of my sunglasses case too! I also carry a few other things like the little Coach pill case, phone, smaller wallet/wristlet, a reusable baggu bag, and occasionally need an umbrella - but even the mini umbrella would barely fit in the bag (I only tried to fit the first few items listed there and it was JAM-PACKED! Plus I have a lot of smaller bags to use for concerts, ballgames, etc., so I don't know how much use the 15 would get, especially considering the price.
Totally understand the rivets 25 calling for you - it really is beautiful, with the contrast of the navy w/oxblood suede interior, plus the brass hardware.

I wish the black 30(31?) would have a more interesting suede interior color, sigh....
But I'm hoping once I see the larger black one in person I will be able to make a choice between the two... the 25 doesn't need to be returned until the 17th, so if I order soon I'll have time to compare!