Most often, the head tube length increases much more than the TT length, between any two sizes, so the larger size will give you a more upright position. Going too large will result in an overly short stem, however.

These days, almost every brand has a more recreational line of "comfort" frames with head tubes that are all 20-30mm taller than their racing frames. With these frames, you can have the taller head tube without getting the additional TT length.

As an example, Trek has the Pro fit, performance fit and women's fit in the Madone series. Similarly, Specialized has the Roubaix and LOOK has the Optimum series.

http://www.trekbikes.com/us/en/bikes..._and_geometry/

My rule is to pay NO attention to frame size numbers. I look at the head tube length, with the headset stack height included, the TT length and the seat tube angle to determine the fit. The TT length without the STA means nothing.