I am looking for a new machine and have started reading about stainless steel boilers being less susceptible to scale. Can anyone expound on the downside of stainless steel vs old school copper?

WLL has an article on this very subject https://www.wholelattelove.com/blogs/ar ... ials-guide As for scaling, I doubt that what you recall reading about stainless not scaling is true. Stainless is resistant to corrosion, which is an entirely different thing. For example, some metals cannot stand distilled or RO water; they pit and corrode. Stainless, on the other hand is far less susceptible to this. We use nearly straight RO water in our stainless kettles and have for many years. They are totally free of any scaling, corrosion or anything else. Actually, they look brand new.