When I use Preview.app to rotate a .TIFF image file 90 degrees, the resulting file is about 10% to 20% larger. All I do is open, rotate, save; there is no exporting or "save as" changes. I've tried this on multiple TIFF files and the behavior is constant.
It's the same file with the same data, so why the size increase?
(2013 rMBP) -- (OS X 10.11.4)