None of them! As you were told on Kendo World, get a decent Japanese-made alloy-bladed iaito.
If you don't want the answer, why ask the question? Again.
What is a decent Japanese-made alloy-bladed iaito? The only reason why the Japanese uses alloy and not carbon steel is because of their country's strict weapons laws. Carbon steel iaito can be turned into a weapon if it sharpened that's why they only allowed weak alloy iaito to be made.