In planting Orientals under the same soil/weather conditions as non-Oriental varieties, I can say with confidence that most Orientals come out milder and with lower nicotine levels than their non-Oriental cousins. The factors that JBD mentions do, of course, come into play. But all external factors being similar, most Oriental varieties intrinsically develop less nicotine. If they are not topped, the leaf nicotine is lower than in topped plants.
Bob