A larger tank (filling a 5lb tank off a 50lb tank) uses less time and money than exchanging 1lb canisters. It also has the ancillary benefit of supporting local welding supply companies and brewing stores than foreign corporations and big box stores.
I don't know if I'd want to consume anything from a welding shop.
This is a valid concern. I did years of homebrew beer before I learned there is food grade and non-food grade CO2. You should not be using non-food grade to carbonate water or beer. It can have oils and other residue in it.
you can also wrench open a sodastream canister, buy a 3lb block of dry ice from a grocery store for $4, crush it, and pour the crumbs into the canister. Youtube has tutorial videos.
The article alleges that sodastreams produce weaker fizz than commercial carbonated water.
I personally haven't found that to be the case, but it seems like there's dozens of sodastream models and maybe I happened on a good one.
My experience is the opposite across a range of models, I always go relatively conservative otherwise it feels like drinking nails.