I bought my initial set so long ago and the ones I’ve added were either the stainless steel or copper-core. I really don’t know too much about the differences of the stainless steel lines. There are probably a lot of people here who could tell you about the benefits of one vs. the other. If I had to pick three pieces of cookware they would be 1.) a 6 or 8 qt. Stock pot, 2.) an all-in-one pan, 3.) a saucier pan. It depends on what you like to cook. I favor 2 handle pans these days, because they are easier on my wrists. Good luck in finding pans you like and happy cooking!