Are they stainless? From what I recall, no. That means they are good in general but don't have the lifespan of anything stainless. You could get a 2.5-3gal corny or...I have seen a few...1gal cornies. Those are very interesting. I have seen them coming out of softserve or milkshake machines, something like that.
Even if those units are just steel and not SS, they would be pretty nice but don't you need a special dispenser? With cornies you have a picnic tap and a CO2 source, no special housing.
Yeah those mini kegs come with a dispenser that you have to open..I haven't actually used one but looked at them at the store...so I am not sure you could actually reuse them because of this.