With CSS Diff you can find all CSS properties that differ between two HTML elements.
To compare elements, activate Chrome Developer Tools (F12) and open "CSS Diff" tab located in the right panel of the "Elements" module (please refer to the screenshot). Next, inspect (e.g. using magnifying glass button) first of the elements that you wish to compare. As soon as it will be selected, CSS Diff will display it in the "last inspected" section. Hit "Compare" button and repeat the whole process for the another element. As soon as two HTML elements will be selected, CSS Diff will show all CSS differences between them.
Source of this extension is available on github: https://github.com/kdzwinel/CSS-Diff
Idea for this extension was inspired by Mike Vanderkley ( http://stackoverflow.com/users/511438/valamas ).