I think that was the Scenera or Touriva that had a cutout/notch on the inside of the shell that made a sharp edge right next to the child's head riding in the seat, not the person next to the seat. I think there was no recall, they did redesign it, though. No news on whether they paid off the family whose kid died of head injuries caused by it, though...
All in all, you'd rather hit nothing in a side impact, or maybe an airbag, but a carseat installed tightly will prevent a lot of sideways body movement and thus injury potential, and plastic's not 'soft', but it's more giving than a door pillar, in the grand scheme of things. The Advocate does make the ride a little safer for next-to occupants, but it also decreases their shoulder room measurably, ironically.