I'll parrot most of the others here.
Sandow has a great character and delivers it expertly. His Mic work has been consistently top-notch since moving to the main roster, and sometimes he's flat out hilarious.
However; Rhodes has also always done very high-quality character work when given something to work with. I thought his "phantom of the opera-esque" gimmick was carried out outstandingly for example. Also his current run since MITB has shown me that he can be a very entertaining babyface as well, and last's night Raw solidified that for me. I'm not sure Sandow could get over so easily as a face.
As for in the ring, Cody to me is one the better hands on the roster while I find Damien's ringwork to be flat out boring, and though the booking doesn't help, it's also not the only problem. He is just a very bland and generic performer between the ropes.
Sandow has been blessed with having one strong character that he has been able to stick to and he has pulled it off more than admirably, but Cody is a much more complete package, and has the ability to be a top-card player for a long time in my eyes, which is a level that I think is above Sandow's capabilities.