Mgallery Ink Hotel for the location an style although the cheaper rooms can be small and it can get busy at breakfast.
Mercure Sloterdijk, it is cheap has nice rooms, lovely staff and near a train station(100m) get's you into the city center within 5-10 min. But it is in the middle of nowhere, as in no tourist attractions and restaurants nearby.
Living in Holland and have stayed in both hotels twice. For a short trip and the feel of real amsterdam i would choose the Mgallery. It is literarily walking distance from a lot of hotspots. ( Anne Frank house, Dam square, Royal palace, red light etc )