Currently we have the option to apply various post-capture effects. Among them there is the possibility to apply a border. This is, however, solid. I find the ragged edges way more useful in some instances (when just a part of a window is selected via a free region select or a "repeat last size/position").
a) Have one radio button for each type of border in the Settings/Post-capture options dialogue.
b) Given the mannic number of borders and border options (especially for the ragged edges style), maybe it would be more practical to always use the last used/selected type of border. This could appear as a drop-down in the settings dialogue (so that between sessions I can check what kind of border will be applied).