Interesting thread. The last time I purchased a bicycle, I was tempted to try a smaller frame, but didn't because I had pretty consistent fit information from both an independent paid fitter and an online fitter that I needed bigger. Next time I will try test riding a smaller size and see how it feels. On another note, I just happened to be looking at the Trek catalogue for 2004 models yesterday, and noticed that inside it makes reference to the fact that LA rides a 58 cm, which is NOT on the small side. He is generally listed about 177 cm tall---under 5 foot 10 inches.
On another note, something to be aware of for any newbies, is that companies measure that seat tube length in different places. Even Trek, Klein and Lemond, which are all owned by Trek, take that measurement in three different places---Trek-center of crank top of seat collar, Klein-center of crank to top of top tube, and Lemond-center of crank to center of top tube. So when comparing a Trek and Lemond, at least in 2004 anyway, a 55 cm Lemond, was similar to 53 cm Trek, in seat tube length anyway. And then of course the top tube lengths and the rest of the bike geometry may be completely different as well. And now comparing sizes across manufacturers is even more complicated with compact frames, sloping top tubes and "effective" or "virtual" sizes. The good news, imo, is that it seems possible through experimentation, changing seat height, seat setback, changing stem length and height, etcetera, to generally get comfortable on two or three frame sizes, up or down, so perhaps you don't have to hit it right on head with the one right frame size for you.
But from what I am reading here, dialing in the right frame size and setup to maximize racing efficiency is a whole another ballgame altogether, and the "right answer" may even change with each race? I suppose a power meter is useful in this endeavor---that you find you are able to generate more power in some positions on certain frame size and setups than others? And what about aerodynamics? Is your most powerful riding position consistent with good aerodynamics or are these two entirely separate things? Sorry to be rambling here, but I haven't got beyond the step of being able to buy a bike and to be able to get reasonably comfortable on it ---which for me was an important accomplishment in and of itself.
The whole process of selecting and setting up a bike to maximize racing efficiency, which racing I am doing occassionally now at the entry level, is a very complicated mystery to me, with seemingly moving targets! I think I like Alienator's take on this subject.
What works for a person is what fits them best, makes them comfy, and encourages them to ride. Big frame, small frame, in between frame.......none of those is empirically better than the other.