unported and with the right speakers i prefer slants. ported or really solid/many plies (9 or more) i prefer straights. some straight cabinets can be too woofy sounding or bass heavy in the wrong tuned note/area. ports help to alleviate this issue if the port is tuned properly.
really depends on the speakers, the cabinet design, the woods, the area im playing, and the volume im playing at.