I am much strong in sumo deads, its definitely much more hamstrings and hips. big mistake when performing them is not having your knees out! and chest up. Sumo also has less strain on the lowerback and the starting position tends to make your back at less of an angle than conventional style.
When i decided to change over to sumo instead of conventional when i was powerlifting, it was because it felt more natural for me to do so. Nowadays, i do both still but more for musclebuilding.