Depends what you are using it for. Currently, the FX-57 would be your choice for a primairly gaming PC. The X2 is better for multitasking because of the second core.
However this may change in the future if game programmers take advantage of the second core.
Intel has an edge in the single core processors for multitasking, including things like photoshop and vid editing. However, in dual core territoy, AMD dominates in practiclly every category