This may be an open ended question but how do you know if a bike fits? I rode 54cm and 52cm Treks and could not really tell a significant difference besides the fact that I felt slightly higher up on the 54cm. On the 54cm, standing with the top tube between my legs, I had just mm's of space but it still felt OK. The 52cm felt OK also but I felt like I was riding a kids bike. I dunno maybe it was my inexperience or psychological.

Note the 54cm Trek (Domane 2.3) was endurance and the 52cm was more of a race oriented (Trek 1.2). I am interested in the endurance geometry.

The associate at the LBS felt that the 52cm fit me best and that my leg angle looked better. He stated that on the 54cm the handlebar is a tad wider also. i did feel like my arms were slightly wider apart. On the 52cm my arms felt straighter.

I can say that sitting on a road bike felt strange after riding hybrid all these years. i am 5'5" to 5'6" with 34 waist and 30 inseam.