It depends on your audience. I enjoy working with copper and brass, but when I want to make something special, I like silver. Gold is not my favorite, but I would like to cast in it some day. I don't know if people know the difference by appearance, but wear and tear shows what is plated versus what is not.
Also, I think it depends on your experience and pocket book. You can make some great looking jewelry without it having to be a fortune.