It's slightly confusing now, as the resolutions are all custom for the liquid retina display size/ shape, but effectively if you want the perfect retina scaling where 4 physical pixels act as one 'looks like' one, text and objects on screen will look bigger on both the 15 and 13 inch MacBook Air than they will on the 14 and 16 inch MacBook pro.
This is because they upped the pixel density for the Pros this generation. Effectively, if the MBA and MBP were both the old 15.4" size/ shape, the Air would have a physical resolution of 2880x1800, which is 4x 1440x900, but it could display as if it were 1680x1050, with just a slight loss of sharpness. This is what the 2016-2019 15" Machines did.
Meanwhile, the MacBook Pro would have a physical resolution of 3360x2100, which is 4x 1680x1050, but it could display as if it were 1440x900, if you wanted everything to be larger/ easier to see and read.