DT's works well for me. As long as you keep refrigerated I belive it lasts a few months or more. I don't notice any vac packing when I open it.
Not sure what ESV is, semi-new to boards. The ESV I know is B-Ionic. If that what you mean then DT's and B do different things. (B being your calcium and trace supplement) DT's is phytoplank. supp.
There's 3 papers on the ESV spray dried marine phytoplankton (SDMP). FWIW, DT's is a live food vs. ESV phyto which is not. DT's also will have a smaller particle size than the ESV product because as the product ages it tends to clump and not disperse as easily.
I am currently using both, I first tried the ESV freezdried phyto when I first met R.Stark at the ESV plant, they are 10 min by car from me, I call them they prepare what I need and I pick it up, he said I will love it, it is good stuff, when I feed the tank everything goes crazy including all my critters they are flying around trying to catch the phyto, I just started using DT'S phyto, picked it up last week, have not noticed a difference in the tank but the critters dont seem as crazy for it as the ESV stuff, cya and gl.