buy the bike you want to ride. You can always change a stem to get a different angle to make the bike fit you the way you want it to so you ride more upright or more aero. If you think in the long haul you will want to ride a racer buy a racer and make it fit you. As you ride you will get to where you will be more flexible and will make minor adjustments an change stem angles/add or remove spacers to the stem.
I am riding an Orbea Orca in a 60 cm frame which is more of a race geometry and I love it, but then I love getting to the top of a hill and blasting down the other side at over 30 mph.