Are disc rotors all the same?

[mistermo]

I have a Cannondale tandem and just bought a set of Hy/Rd brakes to go on it (replacing BB7). I have a second set of wheels without rotors on it and am seeking advice: Do I go to ebay and pick an aesthetically appealing set of SS rotors? Or, is there more to this than I know?

Also, I recall once reading that there's a better brake pad to use with the hy/rd's than the stock pad. What was it?

Thanks in advance.