When compared side by side the quilt ruler and the seam gauge would be virtually identical and a pretty close match to the cutting mat. However, if you were to switch between all four of these while trying to cut same size pieces you would get some minor discrepancies. While it may not show up with short measurements the compound effect would surely be noticeable on larger pieces. Tuck this tip in your back pocket and remember it next time you reach for multiple measuring devices.
Measure twice cut once, but do it all with consistent measuring tools for happier sewing and more polished projects!