Don’t bother looking for a freeware XML Diff or compare tool. Just use Notepad++, you should already have it anyways. One of the plugins it comes with by default is Compare. Green rows show diffs (look for unbolded text to find values or attributes that don’t match), red rows show entirely different formatting and values (including added lines), blue rows show lines removed (left-right compare), white rows are identical. There’s also a NAV on the right hand side which also works as a diff overlay.