I started using Power Elixer because it's doser friendly and does not require shaking before using it.
I was dosing PO4 and NO3 previously but heard a talk from Ryan (BRS) saying that PO4 and NO3 are mostly taken up by algae (some by the corals) but corals mostly utilize amino acids. It made sense, so I made the change and stopped dosing PO4 and NO3.
It's been a few weeks, my sps look awesome, not so much algae growth on the glass. I am happy with the results so far.
Of note, even though Power Elixer instructions say to use the product within one month of opening the bottle, the shelf life is maintained if you refrigerate the leftovers.