But off the top of my head, mainly just that there's a clear visual indicator of the start of lines of text, rather than counting/lining up leading whitespace. In the first example, the strings are all tabbed evenly for the sake of looking "pretty" in the code, but the following would generate the same string, since each line begins after the """:
var xml = """<element attr="content">
""" <body>
""" </body>
"""</element>
""";