I think the commercial yeast producers have an interest in balancing what will work well and what is easy to ship (and what will allow them to exist and profit). Jamil, on the other hand, has an interest and a proclivity toward making award winning beers.
So, given the choice, you can see where my vote lies.
As for milk jugs. They will undoubtedly produce a starter that, one could argue, rival those made in a pyrex flask. I don't think we'll get a definitive answer on that anytime soon. I would always have my doubts, so sometimes I end up throwing a little money toward it so that I can worry about stuff that actually matters.