The plating has very little if any effect. The reason is simple. The plating is thin and galvanically bonded to the bell itself. It is so thin that the resonance of the bell doesn't change. Lacquer could theoretically have a difference because it cannot resonate like metal. I can't say that I have ever been able to notice a difference though. The difference in my playing from day to day is greater than that coating, so it is impossible to say if it is me or the horn, if I notice anything at all.