Your standover is 28" with shoes or without? Put some shoes on and buy the 47cm. But there's really nothing wrong with a slopping top tube. Most of Giant's bikes, including the bowery track bike has what they call the compact road design, meaning they use longer seatpost to make up for the smaller frame. Give's the bike a stiffer feel. Not sure if the smaller kilos have that in common.

If my inseam was 28" i'd still go with the 47cm and use a top tube pad.