Stainless will be easier to clean and have a longer life, but it wll cost a lot more.
I've seen blue revolvers change hands for £30, mine cost me £60. At that sort of price getting a replacement is not too painful on the pocket.
£30 for a bottle of powder that will last months is not a critical expence so should not dictate caliber.
“If a cricketer, for instance, suddenly decided to go into a school and batter a lot of people to death with a cricket bat, which he could do very easily, I mean, are you going to ban cricket bats?” :- Prince Philip said after Dunblane