I have an account with Praxair. They took over Canadian Cylinder and Gas (I think that was what they were called). Once they took over, Praxair started being open on Saturday, which is the only reason I previously dealt with Canadian Cylinder and Gas; I do most my hobby stuff on the weekends, and running out of welding gas on a Friday night can spoil a weekend of choppin'.
I had previously purchased my tank from CC&G and the new account at Praxair seems to honour that system. I had to get a new bottle a couple of weeks ago. They exchanged the empty with a full bottle, but charge for a re-fill. Give Praxair a call for details on being a new customer. Someone told me they prefer to do the rental, which for most hobbiest kinda sucks. I did not shop around for prices. For me, it was all about being able to buy gas on the weekend.
Peace & Gas, Dennis