I'm 5'8 and ended up with a 52 Specialized Allez. Being my first road bike, I'm not too experienced on different fits, however the LBS said I was kind of stuck between the two....and since no 53's are available, I decided to be cautios towards the smaller of the two frames. I feel very comfortable on the bike and have been able to ride it for 2+ hours thus far without discomfort. I feel I made the right choice. For my height I have short legs, don't know if that makes a difference or not...anyway, just my
.02