I would suggest the 23" if for no other reason than the larger frame size will result in the bars being higher relative to the seat than with the smaller frame size, and on a touring bike that is a good thing. I am 5'10 and my 21" (54cm) 520 feels slightly too small, and with the seat properly adjusted, the bars are below seat height which is hard on my neck on long rides. I recently bought a volpe in a larger 55cm and the bars ended up higher than the seat which makes it noticeably more comfortable.