None of them have the same running style. Both Sony and Duke are more complete than Lamar. Jury is still out for me on who is better though.
I feel like Sony is your quintessential RB, if you can create a player for RB, you create Sony. Lamar has that amazing big play ability with his burst, but lacks on consistency with some of the little things you want from a RB. And Duke is just so creative and unique as a RB and overall football player that he is harder to characterize.