Because of the rise of phablets I’ve started working with size classes, orientation and aspect ratio in tandem to determine item placement.
Landscape width breakpoints: 480, 568, 667, 768, 840, 950, 1024, 1280, 1600, 1920
Portrait width breakpoints: 320, 375, 414, 480, 600, 768, 1080, 1200
Aspects (most to least square): 5/4, 4/3, 5/3, 3/2, 16/10, 16/9