Personally I am between two size for sports bra, the smaller ones always "choke" my rib cage, my breathing and lung capacity felt restricted during hard efforts, for most brand, the size up is just way to big.
I tried QK, I can wear both S and M, but the M fit me really well, while I can breath really deep without feeling restricted at all. and it is providing enough support.
also having pocket in a bra is always a Yess!
