I very much prefer the medium size in the bone. I do own the canvas with the patent in blue and it's a great summer bag. But I think you get more bang for your buck with the bone. You can carry it in all seasons.
As far as sizes, I think the large is simply huge for the style. I felt it overwhelmed even the large buckles on the bag. I am a little surprised that you think the large will suit your needs better and must assume you carry more than I do. In that case, I would probably go with what suits your needs too.
Good luck! It's a great bag!