I've don the same thing, I built a small system to run the BBQ grade R-290 through it for a couple days, then recover to a dry clean cylinder, and the PT's match dead on, I used it in allot of old crap air cons after fully explaining and disclosing the ifs to the customer, and to this day they say they never have worked as good as they do now from when they got it!

Only real benefit is convenience of not having to do filtering your self, but they ask one hell of a mark up for that convenience!

All so as stated the little 2 pound (1pound?) green bottles is near pure and dry as one could hope for!

Either way the R-290 whether commercially purified or BBQ grade R-290 home purified beats any man made gas hands down! I'll take the HC fridge in a fire any day of the week over an HFC fridge!