For anyone looking to buy a bike and wants to get serious about cycling, get a professional fitting on an adjustable stationary bike such as the Retul Muve. That way you can get your ideal stack and reach measurements, which are the most important thing to look for in the geometry charts. It really narrows down your selection of bikes. And geometry is really key in getting the best performance. An improper bike fit can dramatically affect your performance and comfort, even if the frame size is right "for your height". Even though Pinarello offers tons of sizes for the F8, none of them would fit me properly because the reach is too short and stack too high. I could "fit" it no problems, but I wouldn't be able to get in a proper position for optimal power and aero efficiency without some drastic tweaks.
If you truly want a bike with a perfect fit without having to go custom, this is the best solution. Only cost me $150 to do that. And if you buy the bike from the same shop that fit you, they will typically match up your fit on the new bike for free. Alternately, you can now buy blind online or used with confidence by knowing if the geometry is correct by simply looking and the charts and knowing your ideal measurments.
Generic sizes like 50, 52, 54 etc... mean almost nothing. You can "ball park" it casually, but if your serious and planning on spending lots of time and money on a bike its not worth risking. Sure, you can always swap stems, change bars, cranks, etc... But you will never feel quite right with the bike. Having to slam stems, run crazy lengths, ridiculously high or low seat heights, seatpost setback, etc... all affects the handling of the bike, aerodynamics, comfort, etc... you can put a bandaid on but it will cause problems and you will eventually just get rid of the bike because of this.
Its alot like finding the perfect shoe. Not only does the sizing differ between brands and models, but there are details like heel slippage, toe box room, height of arch, etc.... Bikes are no different in that respect. If you want to do it right the first time, get a Retul Muve fit before buying a bike. It will save you so much hassle and money in the long run.