In a conventional deadlift, you have a narrow stance, with your feet about 6 inches apart. In order to bend down and pick up the bar without rounding your lower back, you need ample hip and hamstring flexibility. Most guys do not have this flexibility.
Therefore, we recommend that you use the sumo-style deadlift because it requires less hip and hamstring flexibility, decreasing the risk of low back injury. You get all the benefits of a conventional deadlift with less injury risk. If you have experience with conventional deadlifts or a coach you work with, then go for it.