Powder foundation is generally used for oily skin. And liquid foundation is used for more combination skins. However today with the advancement in make-up you get a variety of foundations both liquid and powder for these different skin types. For example you now have oil controlling liquid foundations and hydrating powder foundations. I find with powder foundation you get a very sheer light to medium coverage. Whereas with liquid foundation you can create a dewy natural look with medium to heavy coverage. So really it’s about personal preference regarding the amount of coverage you wish to obtain. I would recommend that you ask for a sample of each if possible and try it out to feel which one would suite your needs.