When forced to choose, I think I'd go with smaller for two reasons: Smaller frames give more standover height and are easier to throw around and maneuver in technical situations. Longer seatposts and stems can compensate for a frame that is too small, but a frame that is too big is just too big.
compare the stack and reach (amongst some other angles/measurements) with the process.
remember to take into account for stem length and bar width. though i also agree with the above comments about sizing small, you'd want to avoid over-compensating the reach with longer stems. the geomtry of bikes now-a-days is often paired with the appropriate stem length to achieve the bike's ideal ride characteristics.