Sometimes these threads degenerate into "theoretical" rambles(opinion/internet statements of "fact") - when all the OP asked for was information on whether a Flowmaster Delta Flow mufflers droned or was quieter then another version. He didn't ask for X pipes or H pipes, long vs short headers. As far as brands, also not his question - yawn!!
The Delta Flow mufflers sound pretty good with and without an H or X though they do mellow some with one. The 50 series is even a bit quieter but still maintains some level of growl.