Doing a 4 week cycle with the trap bar (hex bar) right now. Good stuff. It definitely moves the load right over the center of the feet. Consequently, it works quads and posterior chain (less on lower back) about equally. If you want more lower back work with one, you can lift from a deficit (stand on a 2" box or some such).
For reference, sumo deads are more glute, abductor, adductor-centric. Conventional deads are going to be more spread over the posterior chain (including lower back). Also of interest, a "hack squat" (which is a deadlift with the bar behind your feet, torso upright), is a heavily quad-dominant exercise.
Interesting that as the location of the weight moves front to back, the stress on the body moves back to front.