Difference in Sizing

Instead of going to a large retail store I hit up a bunch of boutique shops because I couldn't get to a mall. I tried on my usual size from all different brands and I definitely notice everything fits so differently. I tried on a bodysuit I loved and I tried two in the same size. One felt slightly smaller but I don't know if I should attribute that to the lace up being too tight or too loose of the 1/4 inch rule.