I have not seen the copper Bazar cups, but would assume that they are probably a little softer than the brass ones. For that reason, I'd go with the brass cups, but I don't believe it much matters. The bigger difference would be between aluminum and copper/brass, and you've already made that choice.
To polish or not to polish, that is the question! I think it depends on your own preferences and your style of performing. If you like all of your props to be shiny and new, then polish away. If you want or need your props to have that "lived-in" look, then don't polish them. I frankly feel that not polishing them is more effective, because it's more natural, but that's just my two cents. Plus, you can use the time you would have spent polishing your cups in practicing your sleights instead! SETHB