Originally Posted by drewtk

Do you have a current road bike? If so, and you're comfortable with its fit, I would take measurements from that and compare it to the bikes you're considering. Even better if you can compare measurements in person to the actual bike.

Even better if there is a fitter you can consult. Bike fit isn't straight forward, and it's worth spending some time and money with a fitter to confirm you're getting the right size.