Both are terrific subs. I think the Hsu subs are a bit more capable in deep bass and the Dynamo subs are a bit more capable in mid-bass. The Dynamo subs have a more sophisticated feature set and amplifier but the Hsu sub has a bit more robust driver. I would say that if you are connecting the sub to a system that doesn't have much in the way of bass management, go for the Dynamo since it has far more ways to control the performance. If you are hooking the sub up to a processor that does have a lot of bass management features, the Hsu sub may make more sense since it offers a bit more raw performance overall. But the Dynamo sub isn't that far from the ULS-15's performance.
