For me, personally, I'd rather buy direct from Power Brands and support the company I'm invested in, especially knowing that $9 shipping won't mean a thing to me once MINE goes off.
That said, what's the difference when sold by Amazon for PB? I honestly have no clue (about a lot of things some may say) but hoping there is someone there that does.
i've bought 8 cases (6 RISE and 2 BOOST) paid no shipping. been handing them all out to people I truck with! we use prime all the time, so it Pays have PRIME!