depends on what pump you buy.
if you buy Avent pump, may be avent milk bag/cup is better (i have avent pump, but i didn't buy its bag/cup). if you buy medela pump, you can consider to bring nurser (bottle) instead of bag or cup to office. it is because all the "thin" bottles are fit for medela pump. moreover, you can reuse it many many times. also, it won't 漏 ma.