[sgt]

Apparently the Dolosse works a lot better for high energy wave environments like coastline of SA etc. They are used here, and I am sure they considered Tetrapods and there was a reason they weren't suitable.

[aaroninsf]

ITT the consensus is they don't actually work better, but, were royalty free.

No idea about either, myself.

[sgt]

Another thing is that you need a lot fewer of them to stack to get the same effect. So cost saving.