For the longest time, I was always going with AMD.
Back then, at equal cost the AMD was faster... or at equal speeds, the AMD was cheaper.

When intel came out with the Core 2 Quad, my Q6600...
That was clearly superior to anything AMD had, and I switched to an Intel product.

When it came time to upgrade, the i7 920 was a lot more powerful than anything AMD offered.

A few years later, the second generation i3's, i5's and i7's were still far more powerful than anything AMD had.
So I've gone with Intel again.

If at some point in the future AMD has the superior product, or a similar product at a much lower price...
And I'm in the market to upgrade, I'd go back to AMD without any qualms.
I was very happy with AMD for four or five systems in a row.
But am also quite happy with Intel for the last three systems.