I bought the white one, which I had wanted for a long time. I thought it held a lot for its size. What bothered me the most was the access. It was inconvenient to open and see the contents without really spreading the opening, plus I pretty much had to take everything out to get something near the bottom. I returned it, not because of the size, but rather because there was some peeling on the front flap. I didn't get another one because I'm now paranoid about it peeling.
If I could design a bigger Willis, I would add about 1/2" to the width, and expand the height and length by about an inch or so. For me, making it a bit bigger would allow me to use it more. I still adore the Willis. I'm thinking of going with the natural, even with the TLC it needs to keep it stain-free.