I would say the metal tube itself is pulled apart at the welds. I would not say the welds themselves broke on either of mine. The welding may have weakened the metal, however. If the rear sway bar wasn't attached to the rear of the bottom spring bracket, it wouldn't do much in regards to performance.
I think the UR rear sway bar is on the right track. I tend to believe their bar will flex some with the rear axle under extreme conditions. There's also more area to weld the smaller, solid bar to the attachment plates. The bar is on the plates flat & welded on.
I think my last one broke as I was pulling into a gas station that has a short steep entrance to climb the curb, crossing the sidewalk there, and entering their parking lot. When you come in somewhat sideways, that rear axle is really torquing.
I had a small gravel pile in my yard, and I had backed my Mirage on the edge of it one day. I personally think that is when my first one cracked. If you avoid things like I just described, the Daox bar may last longer for you. The rubber cushions that were shared may help some, too.
I don't want to deal with adding one during the winter months, but I do like the outcome of having one.