I am also 5'7" with a 30.5" inseam. My torso is long, with broad shoulders and large (for my height) size 10 (45 Euro) feet. I was also torn between a 52 and 54 frame (CAAD9) but ended up with the 54 size. This just felt more comfortable for me and I have less issues with toe overlap.

I would have each adjusted as close a possible by the LBS and go with whatever feels more comfortable.