When I'm comparing frames, I measure the head tube length. Trek finally started including the head tube length in their geometry charts. Head tube length, with the headset, is really what defines the vertical size of the frame.

Trek now has Pro level frames with the traditionally short head tube and lower level frames with 30mm taller head tubes for those who want a less agressive position. The listed frame size will be the same, the non-Pro frame can have a lot taller handlebar.