Understanding the different DIY standpipe systems

[Sea Witch]

I'd like to ask some questions about a couple of the DIY standpipe systems. There's a summary of the best known ones here: the durso, stockman, Herbie, and the Silent Fail-Safe (Beananimal). The last one has more detailed drawings here.

For those familiar with the last 2, Herbie and Beananimal, can anyone tell me what if any is the difference between having the opening to the main pipe containing most of the flow rate facing up or facing down? I mean in both examples that pipe is under water and has a complete siphon (no air), so is there an advantage or disadvantage having one over the other? (opening up or down)?

And for the last one, Beananimal, 1 pipe has 99% of the flow rate down, 1 pipe is the emergency overflow, and the 3rd pipe is open (facing down) with an air opening (siphon break). Why is there an air opening on that one and since it is submerged along with the first one--at the same level--why does water "choose" to go almost all into the complete siphon pipe with only a little going in to the one with the air break? Why does only a little water flow in the one with the siphon break?

Thanks to anyone who can shed some light......