Priefert is the way to go! We have the SO4, and had the chance to purchase a Powder River. Big mistake! First of all, unknown to us, this particular chute had a malfunctioning headgate, it wouldn't release, so now you have a cow in there that needs to get out, and we have had to practically take the headgate apart to get the cow out. Also baby calves could go back through the tailgate because the bars were too far apart.
We called Powder River and the rep told us that they had had a recall on this particular chute, but of course we were too late, so we ended up replacing that. But after working with the Priefert, it was just too much work and harder to handle. We have just purchased our second Priefert.