Depends on what you are doing. The IGP in the fusion processor kills off anything on intels side. However, the processor performance is no where near the core i3 which puts it up against the much older core 2 duo processors.
You're talking about totally different CPUs here. The E8400 was a performance oriented desktop processor. I think it was the second fastest Core 2 Duo released.
The AMD Fusion is designed for low power consumption. Its most suitable deployment is in a notebook for people with modest performance needs, but want more graphical grunt than any intel based notebooks can provide.