From the particular viewpoint of good old raster tile based map apps, I can already recommend the Xperia X Compact due to the lower ppi -- 319 vs. 441 on the Xperia X. 319 ppi should be reasonably usable with @2x map tiles, while 441 would need @3x or @4x, which are not really available anywhere and even if they were, might be slow to download and render. Users of some ports, such as Fairphone 2, should be able to confirm this -- unreadably small text, excessive level of detail and too many tiles vs. the screen size.