Re: powder or concentrate?
I find concentrate to be pointless. It's just ready to feed that you have to dilute. I think powder is the most convenient because you do not have to refrigerate when on the go. I just portion out into these BPA free formula dispensers I have, add water from a bottle I bring with me, shake. With the rice starch one sometimes the nipple would be clogged but it never happened with non-rice-starch formula.
I think ready to feed and powder have their places, and concentrate is the bottom of my convenience list.