I like the Miyata better, especially as it's cheaper. However, if you ride a 56cm, you've got to decide on the 21 (53.34cm) or the 23 (58.42cm), if they're actually in inches. If you're on the larger side of 56cm and have a shorter stem available, maybe the 23 will be the deal, but if you're a reacher on the 56cm, you may be able to make the 21 work. I ride a 56, and "sized" for a 54cm, but have never been able to move down to that size. Moving up, no problem, just avoid standover.

Whatever you pick, remember that you may have to spend the entire day on it, and the latter part of the day is not so fun on a bike that doesn't fit.