Which is the best processing configuration ?

ya friend i7 is the best one.

First I explain you to what is Dual core. Dual core means there is two cores(two processors) in one processor(cpu means processor). Therefore dual core equal to two processors or two cpu's. Now I say the reason The clock speed only show speed not a performance. A quad core processors(latest processors) have high performance in low clock speed and they have a 4 cores (four cpus or four processors). So the clock speed of quad core is less than dual core. For your verification download this pdf of this attached link.

I think the fastest is the core i7

any core to duel u can use