Plating does produce better patterns, IF it's done right. Brister pretty well established that in the tests he describes in his book. Problem is, most plating these days is mostly cosmetic: just washed on.
Agree with Eugene on the hard vs soft shot issue. The less deformed shot, the more stays in the pattern. Retains velocity better, penetrates better. And penetration is the key with shot. Steel is hard but it's also light, and it also sheds velocity very quickly. The fact that it's less dense than lead is what makes it inferior ballistically. You make shot both hard and heavy, like HS, then you've got good stuff. But where lead is legal for upland game, there aren't that many guys who are capable of killing birds farther away than the effective range of good lead loads.
