In thunar missing some advanced options in file operations' dialog, eg. pause action, overwrite only smaller/older files. It should be something like in FilleZilla (http://shutterfreak.net/files/images/11_filezilla_upload_overwrite_set_options.png) and other (usually double panel) file managers.
Sorry for the very late reply ! Thunar was lacking a maintainer for long time. Since Bug #16685 there is a pause button in the copy file dialog. "overwrite smaller/older" in general imo would be overkill ... the options to "overwrite all/one", "renmae all/one" and details on the date on conflicts imo should be sufficient. *** This bug has been marked as a duplicate of bug 16685 ***