It depends on whether you want it loud, or obnoxiously loud, I guess. Facing the openings toward the exhaust stream will result in slightly higher back pressure, and maybe a little quieter operation. I prefer to use a conventional chambered muffler and increase the pipe diameter one size to reduce back pressure. I've got the old-fashioned idea that a muffler is supposed to make the exhaust note quiet enough for me to think, and avoid a noise-induced headache, though. People with irritatingly loud pipes need to paint a big target somewhere on their vehicle so the rest of the world can get a better aiming point!
Jerry
