What brand? //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
But, it depends on the install/box, not the subwoofer itself. 18"s do fine with rock music //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif
Either should be fine and I would definitely suggest a ported box for either. You don't have the cabin gain of a car helping your bass response so you need the extra efficiency of the ported box to get reasonably loud in an open environment.