I think square section is easier to fabricate, you only have to cut the ends square and butt them together to weld rather than notching the ends to fit to round section. Using round horizontally welded to square verticals would be just as easy. If you look closely at what the horizontal components of the gates are made of, it is called "cattle rail" it is rectangular with 1/2 round top and bottom sort of like a flat oval. Most of the modern working yards are made of the stuff here, it is a good product.
I don't think there is much difference in sturdiness, the materials are sized to suit the application, The smooth edges may be an advantage but the cattle rail caters to that also.
It is interesting how the design of equiptment like this evolves in our countries respectively, obviously to satisfy the needs of the users. To see the Australian company Arrow being highly regarded in the US is great. I think the US is the leader in the auto catch head bale design, we just don't see any auto catch here.
Yes I would have liked to have bought an Arrow crush but it was outside my budget however I can't see much that I am missing with this one. They are a fairly new manufacturer and are based at Killarney which is only an hours scenic drive from here on a quite road. They are keen to get any input from me on anything they can improve so I will keep in touch as I often get down there to the Coop.
The big thing is that it has the feel that I was after in operating, some others that I looked at took a bit of effort.
Ken