There are only 10 - 15 beneficial microbial strains in milk kefir made with powder compared with kefir made with live grains, not to mention it is more expensive too! (thehealthyhomeeconomist.com)
Commercial kefir brands typically have far less microbial strains and are not fermented sufficiently long to have the same benefits. (thehealthyhomeeconomist.com)
Ideally you would want a probiotic with live healthy microbial strains. (mypetneedsthat.com)