? Point?
There's no need for a cooperation attack, like you mentioned earlier. Both of them can kill things with the Keyblade, without needing the other to finish the job.
All other Nobodies look like their original selves, Roxas does not look like Sora..
The only difference is hair and eyes. Everything else is exactly like Sora. Hell, his fighting stance in Twilight Town is the same as Sora's KH1 fighting stance.