M4 vs. ZDP vs. XHP: Which one holds the fine edge longest?

[Franz_N]

M4 has held an unbelievably long hair shaving edge in my use, even after cutting quite a bit of cardboard, i was really surprised that it would shave hair after cutting cardboard, any other steel I've used loses that shaving edge cutting cardboard and not even that much cardboard. M4 really is an amazing steel, it is pretty easy to sharpen to. My experience is with the steel is from a Gayle Bradley.