Depends on the task.... And the cost!
While the 680 is "only" a 2/4 it also runs at a significantly higher clock speed (3.6GHz base vs 2.88GHz)
In predominantly single threaded tasks, the 680 should outperform by a decent margin.
All in all though, each have their pros & cons.... and I wouldn't suggest spending the money to "upgrade" from one to the other.
If, hypothetically, you had both of them in your possession, I'd suggest trying them both out in the applications you intend to use them for.
If you have neither, I'd suggest reconsidering in such a dated platform at this stage.