I think the benefits of using a Dumbbell are "better". There's probably less spinal compression. There is also forearm activation.
Not to mention, using Dumbbells, you can also make a lot more hybrid moves like a lunge with a shrug, a lunge with a one-legged deadlift, a lunge with an overhead press, an overhead lunge, a lunge with a side bend, etc.
However, if you use a barbell you can do more of an overload because you're not dependent on forearm strength of any kind.