I understand that you are a user of Intel CPUs because most of my friends in my town, won't even take the idea of buying an AMD. But if you want the most performance you can afford, then stick with the i7, as it has more L2 and L3 cache than the AMDs do.
But if I were you, I'd consider the i5, as it is still a quad core, it consumes less power than the i7 and amd quad/6 cores and it is still a very good processor. It will save you money in the long run with your electricity bill.