I am using a Speedy 30 today, not has a purse, but as a 24-hour overnight bag. I have two outfits, PJs, and cosmetics in it. Carrying a Lana of London as a handbag.
Obviously, this would not work in the winter. But I love this bag in the winter because I can toss in an umbrella, large scarf, gloves, etc.
The 25 has never worked for me. I cannot explain why. I have bought and sold that size about 5 times and have finally given up. But I have 2 BBs and love them. Spacious for a small bag and more low key.
I use my 40 for air travel. It seems to fit under every seat, no matter the plane.
I LoVe the Speedy. There is a size for every need.